The glacier is dying

The Aneto glacier — Spain's largest, and the mandatory crossing on the normal route to the highest peak in the Pyrenees — has shrunk to 30 hectares. It lost 3.6 hectares in the 2024-25 hydrological year alone, making it the third-worst loss on record. Average remaining ice thickness as of autumn 2022 was 11.9 metres. Between 2020 and 2023, the glacier lost ice at -2.6 metres per year — three times the rate of the prior decade. Scientists project complete disappearance by the 2030s. Source: Springer, 2024; The Cryosphere, 2023; DrivingEco, 2025.

This is not an abstract climate statistic. It changes the climbing route. The ice is harder — the FAM (Federación Aragonesa de Montañismo) has issued formal warnings about "hielos muy duros" where crampon points barely penetrate a millimetre. The glacier has fractured, creating new crevasses in locations not marked on any existing map. Rockfall from thawing permafrost along the glacier margins is increasing. On September 15, 2025, GREIM (Guardia Civil mountain rescue) conducted 8 rescues in under 24 hours on the Aneto glacier, including polytrauma, lacerations, ankle fractures, and a rockfall incident during one of the evacuations. Source: lugaresdeaventura.com, 2025.

The GREIM now formally recommends avoiding the traditional Portillón Superior approach to the glacier and using the alternative route via Ibón de Salterillo. Source: elcruzado.es.

Any guide that describes the Aneto glacier as a straightforward snow crossing requiring "basic crampons" is describing a glacier that no longer exists.

The cursed mountain

Local shepherds never called it "Aneto." They called the peak "Malheta" or "Malahita." French cartographers, mishearing the Aragonese pronunciation, transcribed only the accented syllables as "Netou," producing variants "Nelto," "Nettou," and "Aréthon." The cartographer Émile Belloc's late-19th-century hydrological work finally established "Aneto" as the official toponym by 1898. Source: Wikipedia, "Aneto".

Before 1817, the mountain was not even recognized as the range's highest point. That year, Friedrich von Parrot summited the neighbouring Maladeta and realized the peak behind it was taller. Fatal crevasse falls on the glacier — notably the death of a guide named Luchon Barrau — gave the mountain a "cursed" reputation among the local population. Shepherds and valley residents considered it bad luck. The peak that tourists now queue to climb was, for the people who lived beneath it, a place to avoid.

The first ascent came on 20 July 1842, led by Platon de Tchihatcheff, a Russian officer. His party included guides Pierre Sanio de Luz, Bernard Arrazau, and Pierre Redonnet, plus botanist Albert de Franqueville and his guide Jean Sors. They traversed the glacier and crossed a narrow ridge that was subsequently named the "Bridge of Muhammad" — Pont de Mahomet in French, Paso de Mahoma in Spanish. The name's origin is unclear; one theory links it to the Islamic legend of a bridge to paradise, thin as a sword's edge. Source: Wikipedia, "Aneto"; Wikipedia, "Pyrénéisme".

The first winter ascent followed on 1 March 1878 by Roger de Monts. The first ski ascent was 4 April 1904, by Louis Robach and Louis Falisse.

Tchihatcheff's ascent belongs to the broader tradition of Pyrénéisme — a mountaineering philosophy distinct from Alpinism that demanded its practitioners climb, write, and feel simultaneously. The term was coined in 1898 by Henri Beraldi in his seven-volume Cent ans aux Pyrénées. Where Alpinism increasingly emphasised technical conquest and route difficulty, Pyrénéisme insisted on intellectual engagement: geology, botany, cartography, and ethnography alongside the climb. Tchihatcheff was a geologist. Franqueville was a botanist. They weren't just summiting. They were documenting.

The normal route: La Besurta to summit via Renclusa

The standard route is graded PD (Peu Difficile) — alpine mountaineering, not hiking. The distinction matters. This is not a trail with a hard section. It is a glacier crossing with crevasse risk, followed by an exposed grade I-II scramble on an airy ridge. Source: barrabes.com.

The numbers

Metric	Value
Distance	16-22 km round trip (depending on variant)
Elevation gain	1,500-1,800 m from La Besurta
Total time	9-12 hours
Start elevation	1,900 m (La Besurta)
Summit elevation	3,404 m
Technical grade	PD; I-II scrambling at Paso de Mahoma; glacier travel

Segment breakdown

La Besurta (1,900 m) to Refugio de la Renclusa (2,140 m): 50 minutes. Well-marked trail, no difficulty. Most parties overnight at Renclusa and depart at first light.

Renclusa to Portillón Inferior (2,736 m): 1 hour 45 minutes. The trail steepens progressively through the Maladeta massif's north-facing terrain. Cairns mark the path.

Portillón Inferior to Portillón Superior (2,895 m): 30 minutes. The route gains the ridge crest and drops into the glacier basin. This is the transition from hiking to mountaineering. Note: GREIM has formally recommended avoiding the Portillón Superior approach and instead using the alternative via Ibón de Salterillo, due to glacier deterioration and rockfall. Check current conditions with Renclusa refuge staff before committing to either approach. Source: elcruzado.es.

Glacier crossing to foresummit: ~1 hour 45 minutes. This is the crux of the route. The glacier must be crossed roped, with crampons and ice axe. Crevasses are present and their positions change annually as the glacier thins and fragments. Rope up. Do not cross unroped.

Paso de Mahoma to summit: 20 minutes. See below.

Descent: 3 hours 40 minutes to 4 hours. The glacier is crossed a second time. Afternoon softening can change ice conditions significantly from the morning crossing.

First bus

Buses run from Benasque to La Besurta. The first departure is 4:30 AM from Benasque or 5:00 AM from Vado del Hospital (north face approach). Missing the first bus makes a safe round-trip extremely difficult — you need every hour of daylight. Source: barrabes.com.

The Paso de Mahoma

The Puente de Mahoma is a 35-metre exposed ridge between the foresummit and the true summit. Grade I-II. The holds are good. The exposure is extreme — drops of several hundred metres on both sides.

The Barrabes route description puts it plainly: "with very good holds, but with high exposure." The last 7-8 metres can be skipped without major consequence — most parties do not notice the distinction between the end of the traverse and the summit itself. Source: barrabes.com.

The problem with the Paso de Mahoma is not the technical difficulty. It is the queue. In peak season, wait times exceed one hour. You are standing on an exposed ridge at 3,400 metres, in wind, waiting for parties ahead to cross a feature that must be traversed in both directions on the same path. There is no bypass except turning back. Source: lugaresdeaventura.com.

An early start is not just about safety. It is about reaching the Paso de Mahoma before the crowds stack up.

Equipment — what is mandatory

Equipment requirements have changed as the glacier has deteriorated, and getting this wrong has direct physical consequences.

Alpine crampons (10-12 point, horizontal front points). Not trail crampons. Not microspikes. Not Yaktrax. The FAM warning is explicit: the current glacier ice can be "extremely hard" — points barely penetrate. Trail crampons on this surface are not just inadequate; they are actively dangerous because they create a false sense of security on ice that will not hold them. Source: fam.es; lugaresdeaventura.com.

Ice axe. For self-arrest on the glacier and balance on hard ice. A trekking pole is not a substitute.

Helmet. Rockfall from thawing permafrost on the glacier margins. The September 2025 multi-rescue day included rockfall during an ongoing evacuation.

Harness and rope for glacier travel. The glacier has crevasses. Crevasse positions change as the glacier fragments. Unroped travel on this glacier is Russian roulette with a shrinking barrel.

Boots compatible with crampon binding. Semi-rigid or rigid mountaineering boots with heel and toe welts. Soft hiking boots will not hold a crampon under load.

If you do not own this equipment, you can rent it. If you do not know how to use it — specifically, how to walk in crampons on hard ice, how to self-arrest with an ice axe, and how to perform a crevasse rescue — you need a guide.

Guided vs unguided

If you have glacier travel experience, crampon skills, and the equipment, Aneto is a reasonable objective for an unguided party of two or more. Solo unroped glacier travel is reckless regardless of experience.

If you lack glacier experience, hire a guide. Crevasse rescue is a trained procedure. Self-arrest on hard ice is a trained procedure. Reading glacier terrain is a learned skill. The mountain does not grade on effort.

Guide costs

Mountain guides based in the Benasque valley offer guided Aneto ascents. Prices typically range from ~80 to ~150 EUR per person, depending on group size and whether the guide provides equipment. Smaller groups pay more per head; larger groups (4-6 clients) bring the per-person cost down. Most guiding companies include glacier equipment rental in the price. Verify this when booking — some list gear rental separately.

The Barrabes website and local guiding bureaus in Benasque (such as Compañía de Guías del Valle de Benasque) are the standard booking channels.

Refugio de la Renclusa

The Renclusa refuge sits at 2,140 metres on the north face of the Maladeta massif. It is the base for the normal Aneto route. Built in 1916 by the Centre Excursionista de Catalunya (the Catalan Hiking Club), it connects the Pyrenean refuge system to the Catalan Renaixença cultural movement — a detail that matters because it means the hut was built by people who saw mountaineering as a cultural and scientific act, not just a sporting one. Source: Wikipedia, "Pyrénéisme".

Booking

Renclusa is managed by the Federación Aragonesa de Montañismo (FAM). It operates year-round. Prices are valid January through December 2026. Book through fam.es or by phone. FAM/FEDME members receive discounted rates.

In July and August, the refuge fills. Book at least 2-3 months ahead for peak-season weekends. Midweek availability is better. September offers the best combination of availability and stable weather.

Gear rental at the refuge

Buff Entre Refugios operates a gear rental service at Renclusa itself. You can pick up crampons, ice axes, and helmets at the hut and return them after your climb. This eliminates carrying technical gear from Benasque or renting in town and hauling it up the approach trail. Source: buffentrerefugios.com.

If you are flying into Barcelona and taking public transport to Benasque, not needing to carry or check crampons and an ice axe simplifies the journey materially.

Alternative: sleep in Benasque, take the first bus

If the refuge is full, sleep in Benasque and catch the 4:30 AM bus to La Besurta. This adds ~50 minutes of approach to the Renclusa trail junction. The trade-off: you start later than parties who departed the refuge at first light. On a mountain where the Paso de Mahoma queue is the rate-limiter, an hour's delay means an hour's wait at the crux.

Benasque: the basecamp

Benasque (1,138 m) is the gateway town. Hotels, hostels, apartments, campgrounds, a well-stocked supermarket, and two mountaineering shops that rent glacier equipment.

Gear shops

Shop	Rental	Notes
All Radical Mountain	Yes — crampons, axes, helmets	Full alpine outfitter since 1992. allradical.com
El Ribagorza	Yes — crampons, axes	Ski and mountain rental. elribagorza.es
Deportes Flap	Yes	Castejón de Sos, at the valley entrance. General mountain sports.

Getting to Benasque

From Barcelona (BCN): Bus daily except Sunday via Barbastro with connection. Total 4-5 hours. ALSA operates the Barbastro sector. Sunday service is poor — plan accordingly or rent a car. Source: benasque.org.

From Toulouse (TLS): ~2.5 hours drive via A64 and D125 through Bagnères-de-Luchon, then over the mountains into Spain. No practical public transport on this route.

From Zaragoza (ZAZ): ~3.5 hours drive via A-2 and N-260. Zaragoza airport has limited international routes (Ryanair, Vueling, Wizz Air to 11 destinations). Source: flightsfrom.com/ZAZ.

Barcelona is the best international gateway. Toulouse is the best if you are already in France.

Weather windows

The Aneto summit season runs from late June through September. Within that window, not all months are equal.

Late June to mid-July: Most stable conditions. Snow has melted from the approach trail. The glacier is at its firmest (not yet softened by a summer of warm days). Daylight is longest. Crowds are building but not yet at peak. This is the best window.

Late July through August: Peak crowds. Hot valley temperatures (30C+) trigger permafrost thaw above 3,200 m, increasing rockfall and crevasse widening. Afternoon thunderstorms are the signature Pyrenean hazard — clear sky in the morning, cumulus buildup from noon, storms from 14:00 to 17:00. Be off the summit and off the glacier by 13:00. Source: hikepyrenees.co.uk.

September 1-25: The overlooked window. Crowds drop 60-70%. Afternoon thunderstorm risk decreases compared to August. Temperatures are comfortable. Renclusa and most facilities remain open through September 20-30. Trade-off: shorter days, colder mornings (3C at 2,500 m), possible early snow on the approach. The 8-rescue day on September 15, 2025 was attributed to glacier conditions degraded by a warm summer — September does not eliminate glacier risk.

October onward: Refuges closing. Winter conditions returning to high altitude. Not a viable window for most parties.

Rescue

Mountain rescue on Aneto is handled by GREIM (Guardia Civil — Grupos de Rescate e Intervención en Montaña), with stations at Benasque and Boltaña. Two helicopters are available — one permanently based in Huesca, a second stationed in Benasque during summer months. Medical personnel from the Aragonese Health Service deploy with rescue teams.

Rescue in Aragón is free. Regardless of federation membership, regardless of insurance status. The GREIM mountain rescue service is publicly funded. "En Aragón, al contrario que en otras comunidades, en caso de precisar un rescate en montaña todo este despliegue de medios es un servicio gratuito para el rescatado o rescatada, esté federado/a o no." Source: montanasegura.com.

This is a significant difference from France, where helicopter rescue is billed to the patient (1,500-5,000 EUR without insurance), and from the Dolomites, where non-injury helicopter evacuation costs 90-120 EUR per minute of flight time. Aneto sits on the Spanish side. If you fall on the Spanish side, rescue is free. If you somehow end up needing rescue on the French side of the ridge, it is not.

Emergency number: 112 (universal European emergency number, connects to SOS Aragón in this region) or 062 (Guardia Civil direct).

The route the GREIM recommends you avoid

The traditional normal route accesses the glacier via the Portillón Superior (2,895 m). This has been the standard approach described in every guidebook for decades.

As of 2025, the GREIM formally recommends avoiding this approach. The reason: glacier deterioration has left the Portillón Superior access zone exposed to rockfall from thawing permafrost, and the glacier edge at this point now features large crevasses that did not exist when the guidebooks were written. Source: elcruzado.es.

The recommended alternative is via Ibón de Salterillo, which approaches the glacier from a different angle and avoids the worst of the rockfall zone. This is not yet reflected in the Cicerone guidebook (6th edition) or in most online route descriptions. Ask at Renclusa for current conditions and the recommended approach before your summit day.

What you are actually climbing

Aneto at 3,404 metres sits below the altitude where most non-acclimatized hikers experience significant problems. Compare Mont Blanc at 4,808 m or Kilimanjaro at 5,895 m. On Aneto, altitude is unlikely to be your limiting factor. The glacier and the Paso de Mahoma are.

The trade-off is that the glacier is dying. Within a decade, the mandatory glacier crossing may not exist. The Paso de Mahoma will still be there — rock does not melt at 3,400 m — but the route's character will change fundamentally. What is currently a glacier mountaineering route will become a scramble over moraine and loose rock where ice used to be.

If you want to climb the highest Pyrenee with a glacier under your crampons, the window is measured in years, not decades.

What's changed recently

"Basic crampons and an ice axe are sufficient." Corrected: Trail crampons and microspikes are explicitly flagged as dangerous on the current glacier surface. Full alpine crampons (10-12 point) plus ice axe, helmet, harness, and rope for crevasse rescue are the minimum standard. Source: fam.es.

"The standard route goes via Portillón Superior." Corrected: GREIM now recommends the alternative via Ibón de Salterillo due to rockfall and crevasse hazards. The Cicerone 6th edition does not reflect this change. Source: elcruzado.es.

"Aneto is a long hike." Corrected: It is graded PD — alpine mountaineering. The glacier crossing and the Paso de Mahoma are not hiking terrain. Treating this as a hike is how the September 2025 multi-rescue day happened.

"You can do it solo." Corrected: Solo unroped glacier travel has crevasse-fall risk with zero self-rescue capability. Minimum party size for the glacier is two, roped together, with crevasse rescue knowledge and equipment.

"August is the best month." Corrected: August has the highest rockfall risk (permafrost thaw), the worst crowds (hour-long queues at the Paso de Mahoma), and the most aggressive afternoon thunderstorm pattern. Late June or September are better windows for both safety and experience.

What to do with this

Book Renclusa 2-3 months ahead for July-August. Midweek is easier. September is the best combination of availability and conditions.

Rent gear at Renclusa via Buff Entre Refugios if you are flying in without technical equipment. Pick up crampons, axe, and helmet at the hut. Return after descent.

Catch the 4:30 AM bus from Benasque if not sleeping at the refuge. Every hour matters — the Paso de Mahoma queue builds through the morning.

Check the recommended glacier approach with Renclusa staff the evening before your summit attempt. The route may have changed since the last guidebook was written. It may change between seasons.

Carry a helmet on the glacier, not just for the Paso de Mahoma. Rockfall from marginal moraine is the hazard most parties underestimate.

Be off the summit by 13:00. The Pyrenean afternoon thunderstorm pattern is real. Getting caught above 3,000 m in an electrical storm on an exposed ridge is a survival situation.

If you lack glacier experience, hire a guide. 80-150 EUR per person. The guide provides the rope, the crevasse rescue skills, and the current route knowledge. This is not an upsell. It is a risk management decision on a route where 8 people were rescued in a single day.

Aneto (3,404m) — the glacier crossing on borrowed time