And I'd be amazed if someone knew what I was looking for, since this is the best description that I can give of it from what I remember. Last I saw it was a couple of years back.
It started out (it was a PvP server) with these guys in a stone and gravel/cobblestone room with a bunch of beds, and it took them to the main arena by rail. The main arena was basically a normal survival world, but enclosed by glass. The players then had one night (Minecraft time) to gather resources and either build as high as they could go, or somehow give themselves and their allies safety. At the end of the timer, the glass walls would disappear, and it was either sand or lava - would come in, and the players would have to try and survive it.There were players that turned to PvP to try and secure the highest tower and everything.
I know that it's just a general lava wars server, but I'm trying to find that specific video as I wanted to show a friend it, since that one in particular gave me an idea for an event that I'd like to run in a clan that I'm in.