Interesting article on Kuro5hin on exploring abandoned buildings:
It's the dead of night, and I'm stumbling through dense undergrowth, a weak pen torch lighting the way. Brambles tear at my clothes and bare arms. Ahead, Monty navigates with a stronger beam, and leads me and Pi up a steep incline. I give up all pretence of looking after my clothes and scramble up on my hands and knees, the torch held in my mouth. I slide down the other side on my arse into a broad trench. "Watch your step, it's along here somewhere," says Monty. We walk slowly, scanning the floor with our torches, and there it is - a featureless black hole in the leaf litter, just three feet across. With apprehension I realise that now I've come all this way, I'm going to have to climb inside.
This kind of appeals to the archaeologist in me, but I think these buildings would mostly be dirty, scummy and empty.