Urban exploring

This is so cool, I love these photos! I've never heard of 'urban exploring' or 'urbex' before, but I accidently saw an article in the newspaper about a Dutch website; www.urbex.nl . They say:

"Urban exploration, urbex or UE, is the examination of the normally unseen or off-limits parts of human civilisation. Abandoned industry, hospitals and even military bases.
Armed with flashlight and cameras we search for natural decay, as nature grows trees on the roof and weeds in the carpet."