Some of my friends do "Urban Exploring" and have taken me on a few trips. I have gone to some really freaky places, but I find it kinda sad and interesting that some buildings are just being left to rot.
My fave place that we visited was a small hospital that hadn't been used in years. It was built to cater for injured people involved in World War II. There were actually two really old iron lungs just left there, and all the doors to the building were just left unlocked!
Here is a pic that another explorer took of one of the iron lungs: