Big Tunnel
The underground network the Yellow route opens. Walking into it is what awards the medal.
Big Walk Big Tunnel Achievement: Enter a Big Tunnel
Open the underground tunnel network through the Yellow route, then walk into one of the network’s own entrances. Opening it is not the achievement trigger.
Big Tunnel is attached to the tunnel network the Yellow route opens. The trigger is entering one of its tunnel zones, not placing the key or opening the gates.
- Achievement
- Big Tunnel
- Official requirement
- Enter a big tunnel
- Verified trigger
- Enter a tunnel entrance zone
- Requires
- Tunnel network open
- Not the same as
- Riding through a railway tunnel
Big Tunnel
Quick Answer
Finish the Yellow route so the tunnel network opens, then walk into one of the network’s entrances. Big Tunnel is awarded by entering a tunnel zone, so placing the key, opening the gates or riding a Train through a railway tunnel is not the same thing.
Getting inside is the whole requirement.
Show Me the Entry StepBig Tunnel Not Unlocking?
This is one of the gameplay achievements. See the full achievements list
Where Are You Stuck?
Pick the line that matches your run. The tunnel network and the railway are different systems, and only one of them carries this achievement.
The Tunnels are still locked
That is a progression problem, not an achievement problem. Finish the Yellow Key route so the network opens.
Open Tunnels GuideHow to Unlock Big Tunnel
Three steps. Only the last one is the achievement trigger.
1. Unlock the Tunnel Network
If the tunnels are still locked, finish the Yellow Key route first. That is what opens the underground network.
Open Tunnels Guide2. Go to an open entrance
Use any open access point of the network rather than travelling back to one particular gate.
3. Walk inside
Move through the entrance and into the tunnel. Getting inside is what registers the Tunnel medal.
If the achievement has not appeared, walk in through another open entrance before replaying the whole Yellow route.
What Actually Triggers Big Tunnel?
Big Tunnel is attached to the tunnel network itself, not to the Yellow Key.
The achievement comes from a trigger zone sitting in the tunnel itself. The Tunnel medal is awarded when your player enters that zone, which is why opening the network and earning the achievement are separate states.
- Medal
- Tunnel
- Attached to
- The tunnel entrances
Verified game-data detail
You do not need any of this to walk into a tunnel.
- Component
- MedalZone
- Native event
- MedalZone.OnEnter / OnEnable
- Trigger surface
- The tunnel network’s own entrances
Big Tunnel or a Train Tunnel?
Two different tunnels share one word, and only one of them is this achievement.
Railway tunnel
Part of the Train route. Riding the Train through one belongs to the railway and does not award Big Tunnel.
Open Train GuideWhich Tunnel Entrances Count?
Use an entrance that belongs to the tunnel network the Yellow route opened.
The network has four coloured access points — Red, Green, Blue and Yellow — and they are all part of the same system. Nothing in the achievement condition names one of them, so you do not have to travel to a particular colour to get it.
A cave, a hole in the ground or any other underground corner is not the same as an entrance of this network.
Show Tunnel Access PointsBig Tunnel Not Unlocking?
Work down the list. The first line that is still true is the one to fix.
1. Is it actually part of the tunnel network?
A railway tunnel, a small cave or an ordinary underground room is not an entrance of this network, and none of them carries the Tunnel medal.
2. Is the network open?
If the entrances are still locked behind the Yellow route, this is a progression problem rather than an achievement problem.
Open Tunnels Guide3. Did you walk inside?
Stopping at the mouth, standing under the arch or opening the gate leaves you outside the zone. Keep going until you are inside the tunnel.
4. Try another open entrance
The entrance zones belong to the network rather than to one gate, so walking in through a different access point is a reasonable way to retry the entry.
5. Platform achievement delayed?
The in-game medal and the Steam or PS5 notification can update at different times. Check your platform achievement list before replaying the whole Yellow route.
What Is Not Required
These come up often, but none of them is needed.
Walking the whole tunnel
You do not have to come out the other side. Getting inside is what counts.
Every outlet in the network
One entrance is enough. The achievement is not a tour of the network.
One specific colour
Red, Green, Blue and Yellow access points belong to the same system, and no colour is required.
One specific entrance
The Yellow route unlocks the network, but the achievement does not send you back to one particular gate.
A set time inside
No number of seconds is required. Walk in far enough for the tunnel zone to register you.
Big Tunnel FAQ
¿Cómo se desbloquea «Un gran túnel» en Big Walk?
Abre la red de túneles con la ruta amarilla y luego entra caminando por una de sus entradas. La medalla Tunnel se otorga en cuanto estás adentro.
¿Basta con abrir la red de túneles?
No. Abrir la red y conseguir el logro son estados distintos: la zona de entrada activa la medalla, no el desbloqueo.
¿De verdad tengo que entrar al túnel?
Sí. Quedarte en la boca del túnel o frente a una puerta abierta te deja fuera de la zona.
¿Cuenta un túnel del tren?
No. Los túneles de ferrocarril pertenecen a la ruta del tren, mientras que «Un gran túnel» viene de la red subterránea que abre la ruta amarilla. Guía del Tren
¿Tengo que usar la entrada de túnel amarilla?
No. La ruta amarilla es la que desbloquea la red, pero el logro no menciona una puerta específica.
¿Importa el color del túnel?
No. Los cuatro puntos de acceso de colores forman parte del mismo sistema y no se exige ningún color.
¿Tengo que recorrerlo completo?
No. Llegar al otro extremo no forma parte del logro; estar adentro, sí.
¿Tengo que visitar todas las salidas de los túneles?
No. Con una entrada basta.
¿Por qué no se desbloqueó «Un gran túnel» cuando abrí la puerta?
Abrir la red es el requisito previo, no el activador. Aun así tienes que entrar a un túnel. Guía de los túneles
¿Por qué no se desbloqueó «Un gran túnel» después de que entré?
Comprueba que el túnel pertenece a la red y no al ferrocarril; después adéntrate más o prueba otra entrada abierta.
Related
Tunnels Guide
How the network opens, where its access points are, and why they will not open.
Yellow Area Walkthrough
The Yellow route that ends at the tunnel destination.
Train Guide
The railway and its own tunnels.
Big Makeover
The colour achievement found inside the tunnels.
Interactive Map
Show the tunnel network on the map.
Achievements
All 12 gameplay achievements and the platform layer.
The Big Tunnel entry trigger and the network’s four access points last verified on 1 October 2026.