Love the photos - and I've thought several times of getting involved with a bit of Urban Exploration.
However, in the 35 years I've been working in insurance (insuring owners of building portfolios where some of them are unoccupied / derelict / awaiting demolition / refurbishment), I've seen several serious injury claims where trespassers have sued building owners for compensation when variously, falling down unlit stairs, falling through holes in floors, falling through skylights, ripping clothes on exposed nails, electrocution from loose / unprotected wires and a load of other stuff. In the UK, building owners still owe a significant duty of care to trespassers for any injuries sustained as a result of the building / land owner's legal negligence.
It sorts of puts me off as I am a clumsy sod at the best of times