I love abandoned places: Some of my happiest times have been spent exploring old factories, houses, hotels.... They can be quite eerie, but there's also a strange sense of sadness about them, as though they're stuck in time just waiting for the people to come back.
Some of the ones I've been to have been amazing: There's a couple of abandoned hospitals in huge areas of land that are crying out to be used, but sit there slowly rotting away. In another place I went into, there was a set of offices with the personnel files still in the file cabinets.