How to make sure my player doesn't climb moutains (online fps)

hi i am working on first game in unity and i just started build the map and the town im building has moutains and i am woundering how to get my player (defualt 1st person prefab) to not climb moutains

the map looks like this


please help .w.

There is a parameter in Character Controller component which describes maximum walkable angle of surface.

You could use the old fashion way, invisible walls.

thanks