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L'étang aux carpes vue du ciel

Treks / France

Les 25 Bosses (Fontainebleau)

France · Nearest city: Paris

TypeDay hike
Days1
Distance≈ 16 km
Climbing≈ 900 m
Highest point144 m

A famous training loop in Fontainebleau Forest near Paris: 25 sandy, rocky 'bumps' that add up to a surprisingly hard day.

Fitness Demanding
Best seasonAll year

Watch out: Short, steep climbs over boulders. It's harder than the low altitude suggests.

Why people choose it

Parisian trail runners and trekkers use it as training: 25 short, steep sandstone climbs that add up to a surprisingly hard day.

What makes it different

  • Reachable by train from Paris
  • Famous boulders used by climbers worldwide
  • Perfect training for bigger treks

Route options

There is rarely just one way to walk Les 25 Bosses (Fontainebleau). These are the main choices people make.

  • Raccourci du rocher Cailleau (0.1 km): an alternative to part of the main route.
  • Sentier des 25 bosses Variante du Diplodocus variant (1.1 km): an alternative to part of the main route.
  • Variants are shown as dotted purple lines on the map above, as mapped in OpenStreetMap. Some are harder or more exposed than the main route: check conditions locally before you pick one.

Similar treks to consider

Trolltunga Norway · 1 day · 27 km A long day hike to the famous 'troll's tongue' rock ledge high above Ringedalsvatnet lake. Ben Nevis Mountain Track United Kingdom (Scotland) · 1 day · 17 km The main path up Britain's highest mountain from Glen Nevis. Long and rocky, with a summit often in cloud. Cinque Terre: Sentiero Azzurro Italy · 1 day · 12 km The famous Blue Path linking the five villages of the Cinque Terre on cliffs above the sea. Short, but...

Before you go

Some of these are affiliate links: if you book through them we may earn a small commission, at no extra cost to you. We only list services that fit this trek.

Phone and data

Phone plans from the EU and EEA roam here at home prices. Coming from the US, UK or elsewhere? A Europe data eSIM is usually far cheaper than roaming.

Europe eSIM on Airalo

Expect long stretches with no signal on the trail. Download offline maps and our GPX before you start.

Insurance that covers this trek

Most travel insurance includes hiking at this height. Check that hiking is listed and that medical evacuation is covered.

Rescue is not the same as evacuation. Travel insurance usually pays to fly you to hospital, but not always for the search and rescue itself. Read the policy's "search and rescue" section, or join an Alpine club: membership of the Austrian Alpenverein (it has an English-speaking UK section) includes rescue cover of up to €25,000.

World NomadsHeymondoSafetyWingTrue Traveller

True Traveller sells only to UK and EEA residents. Always check the altitude limit and your country of residence in the policy wording. Our trekking insurance guide explains what to look for.

Camping and where to sleep

Rules vary. In many mountain areas a bivouac from dusk to dawn is tolerated, but national parks have strict zones. Check the park's rules before you pitch.

Rules change and differ between parks. Check with the local park or tourist office before you pitch a tent.

Route map

Download GPX

Map layers load on the live site. Use the overview below meanwhile.

Trail from OpenStreetMap (15.0 km) Route variant Start / finish Stop on the way Nearest city

Switch between Topo, Satellite and Street layers with the layer button, and turn on the marked hiking trails overlay. The trail line is the OpenStreetMap hiking route and may differ from the variant you choose. Always carry a proper hiking map on the trail.

Stops: Fontainebleau

Simple overview map
FontainebleauParis25 kmN

Step by step

  1. Months before

    Plan and book

    • No bookings are needed for most people. Choose a day with a good forecast.
    • Best time to go: All year.
  2. 6–12 weeks before

    Train and test your gear

    • Take the readiness quiz to see how many weeks of training you need.
    • Break in your boots and train with the pack you'll carry.
    • Tick off the packing list to see what you still need.

    Readiness quiz · Packing list

  3. Getting there

    Travel to the start

    • Most people start from Paris.
  4. On the trail

    Walk it

    • Start early and set a turnaround time. Be back down before the weather turns or daylight fades.
    • Carry water, food, a warm layer and a rain jacket even on a sunny day.
  5. The finish

    Get home

    • It's a one-way route, so plan your transport back from the finish in advance.

How the season changes things

Best time: All year

April to May

Spring

Fresh green forests and cool, comfortable temperatures. Paths can be muddy.

Bring

  • Waterproof boots
  • Light rain jacket
  • Warm layer

June to August

Summer

Warm and sometimes hot, with thunderstorms and busy weekends at popular viewpoints.

Bring

  • Water and sun hat
  • Rain jacket
  • Go on weekdays if you can

September to October

Autumn

Beautiful autumn colours and quieter trails, with cooler mornings.

Bring

  • Warm layer
  • Headlamp
  • Waterproofs

Be ready for

Easy scrambling

A few short hands-on sections. Keep your hands free and your pack tidy.

What you'll see

3 photos taken on and around the route by Wikimedia Commons photographers. Tap one to see it bigger.

L'étang aux carpes vue du ciel
Near Fontainebleau
Near FontainebleauLes Grandes Vallées @ Laris qui Parle

Gear for the Les 25 Bosses (Fontainebleau)

Hiking boots Top pick: La Sportiva Ultra Raptor 3 Mid GTX Trekking poles Top pick: Black Diamond Alpine Carbon Cork Rain jackets Top pick: Patagonia Torrentshell 3L

Photo credits: L'étang aux carpes vue du ciel by Nyyynon, CC BY-SA 4.0, via Wikimedia Commons; View near Fontainebleau by Jerome Bon from Paris, France, CC BY 2.0, via Wikimedia Commons; Les Grandes Vallées @ Laris qui Parle by Rémih, CC BY-SA 4.0, via Wikimedia Commons. Photos resized for the web. Figures are approximate and vary with the variant you choose.