You guys made me go to Wookieepedia.
http://starwars.wikia.com/wiki/Death_Star
With the exception of the crust, the station’s entire interior space was uninhabited, and housed the hypermatter reactor, hyperdrive, sublight engines, and the station’s superweapon.
I can vouch for this I was actually one of the engineers that worked on the Death Star.
Wow, a survivor!
See, it pays to always be late to work. I wasn’t in the office that day.