Abandoned love hotel
.... call it "urban exploration," "modern archaeology" or what have you, but it's a fairly common pastime among certain people with a taste for adventure, and as a result there're dozens of sites in Japan devoted to information on haikyo (literally "ruin" but usually taken to mean "abandoned area"). Some of them have gotten faily popular, to the point where Toru Kurihara of Haikyo Explorer has published a bestselling book based on his exploits.