Churches, Rectories, Nunneries
All manner of religious structures have been forsaken in the wake of the church sex-abuse scandals. This has left the pious without a place to worship, but has provided a dearth of new and exciting structures for explorers to enjoy.
Commercial structures including company headquarters, office buildings, and light manufacturing. Despite the modern trend towards the construction of soulless cube-farms, many older commercial structures were much more ornate, attempting to convey a sense of grandeur and continuity to customers.
Many consider hospitals the holy grail of exploring. Some explorers concentrate on hospitals and little else. While I enjoy photographing all types of abandoned structures, there is definitely something compelling about hospitals which cannot be experienced in other types of structures. Perhaps the life and death struggles, the human drama, which occurred within the walls of these places have left something behind. Asylums, in particular, have a controversial and interesting history which makes them a particularly interesting subject for photography.
Various houses of lodging and leisure. Abandoned hotels can be a hilarious window into the decor of the past. Nowhere else are the trends and fads of the past as apparent as they are in hotels. It is always interesting to explore these structures because they provide a very clear contrast with what has changed between the recent past and today.
Industrial abandonments are probably the easiest type of structures to find and access. Nonetheless, over the years they have also become one of my favorite types of structures to explore. Old mills are usually easy to access and relaxing to explore. Larger industrial abandonments often contain interesting old equipment and, in some cases, used to manufacture products that we have all used at one time or another.
Military Installations
The US Military's geographical footprint has changed much since the cold war, leaving many interesting sites behind. I find cold war era history and installations fascinating...they are usually filled with tons of interesting equipment and relics to pick through.
Miscellaneous sites which may not fit in another category. From nursing homes to housing projects to subway tunnels to amusement parks.
No matter what city you visit, there is almost always an abandoned school somewhere. Sometimes there are many of them. Unfortunately, it seems when hard economic times hit schools are one of the first institutions to suffer.
Theaters and other performance spaces. Nowhere else but in these structures is the contrast between grandeur and decay so apparent!
Transportation Infrastructure can be extremely compelling to explore.