Old news if you paid attention to our liveblog of the PvP panel at BlizzCon (or if you read through Zach's great analysis of the news we got there), but Blizzard is adding two new Arena spaces to the game, and they've created an official page to show off the new designs and mechanics in each.
The Ring of Valor is a new space in Orgrimmar -- it features an elevator that rises up to a starting position that leaves players in close proximity, and then there is a set of fire obstacles and two moving pillars that can be used to as many tactical advantages that you can come up with. The other space, the Dalaran Sewers, also mixes in a few line-of-sight tricks, including a periodic waterfall that blocks LoS and a raised platform in the middle that can only be reached via two sets of stairs on diagonal sides.
Personally, I think the new mechanics are exciting, but then again I've played maybe four Arena matches in my life -- word I'm getting from most of the Arena players I know is that these changes add a little too much RNG to the maps (considering the all the obstacles are timed, they're not really random, but that's just what I think). What say you, Arena players?