So I usually don't look stuff up, but I've been stuck here since last night and can't figure it out.

I just found the witch's apprentice, telling me to find the witch.

I think I'm supposed to enter Hiberheim through this gate, but I can't find a button, pressure plate or anything to open it. Any ideas?

It's the big door/gate adjacent to the waypoint portal in Hiberheim cave.

Screenshot: http://i.imgur.com/wup88x9.jpg