Look down over the railing and you'll see water. Throw a cryo bomb into the water to make a raft and then jump on. Use the batclaw to pull your raft along but make sure you let go and duck before you hit the wall. When you come out on the other side, use the bat claw to pull you towards the saws and then just jump up to the ledge above. Make a new raft on the other side and use the rings around the outside to stay away from the saw in the middle. Bring the raft to the far side and hop off again.
Climb up and look through the window. Glide through the window to start the fight. Keep a finger on your baterangs and the other on your counters. Those will save you big in this fight. Use the baterangs on the people trying to get weapons and counter everything they throw at you, which will be a lot. And watch out for the armored guy. He's the only special type of enemy here.
..."And why did it end in a church!?" Best line ever!
Go through the only door in the room and do a takedown on the unarmored guy. Then just stun the armored guy and take him down. Release the guy if you want but if you stick around for too long, he'll attack you. Blast a hole in the wall and go for a raft ride. Use the anchor points on the wall to pull yourself away from the saws and then use the other up ahead to pull yourself under the wall. On the other side of the wall, you will need to pull yourself back the way you came and off to the side. Get off the ice and onto dry land, then use the line launcher to get across to the other side.
From there, take a right and make another raft. Climb up on the ledge ahead. This part is a little tricky. You need to throw a remote control baterang through the hole in the door ahead, have it fly through the sparking electricity in the next room and then it needs to turn around and go into the other door and strike the panel in the small caged in room. It takes a few tries and some practice. On the other side, make a raft and be on the lookout on the right for a ledge to grapple up to. Once you get there, look for a security panel. Hack that and a draw bridge will drop for you to cross. Cross the draw bridge and take a right. Head for the double doors and eventually go through them.