Stuck in Road to Monestary

[BigBDLH]

Right at the beginning of the level I killed all enemies. Now I dont know what to do.

I discovered the tunnel on the right and all walkable places around the tower on the plattform. If i follow the needle on the compass it leads me into the tunnel, right at the beginning of the tunnel it turns right into the opposite direction.

So my guess is to either find a way to open the grate at the end of the tunnel or find a way to reach the plattform with the tower. What do I do? Pls help a blind man out .