The Iron Cage

Here's a nice and versatile dungeon feature.

It could be a cage trap set to drop on the unwary.  It could be a cage containing a rare and expensive monster that, whoops - the party just stepped on a release mechanism and now it's escaped.  Or it could contain that lost princess you've been hired to find.

The two portcullises crafted as hallway blockers can easily be pressed into service with this feature to make an even cooler looking cell block.