Grimrock

So there's a pit, and in this pit there is a gate with a lever behind it and another gate which leads to a room with what looks to be a piece of armor. From what I can tell I need to drop down from above. It looks like I drop in from that room with all the pits with the portal in the middle. I'm assuming I clear out the portal and open up the hole beneath it and drop down. There's also a switch on the wall that I can't reach.

I'm completely stumped. Is this something I should come back to later or what?