When you encounter Ishtvan, you will see the two chains supporting him. You'll need to back track, following the chains, to find the areas where you'll disconnect them.
For the first chain, go back to the room you came from, you'll see the chain coming out of the wall into a stone. Climb up onto the ledge and disconnect it (There is also a relic here).
For the second chain, face Ishtvan. Behind you and to your right is a broken staircase. Climb the chain that is hanging here, and continue up to the suspended area. The second chain is over the archway to your left. If you have trouble, just look down at Ishtvan and follow where the chain goes.