Kusatsu may be best known for hot-springs and skiing, but it's also home to the Nettaikan, a dome filled with a wide range of tropical animals. They have crocodiles, iguanas and Gila monsters; plenty of snakes, including boas and golden pythons over two meters long; cuter animals like lemus, marmosets, capybaras and meercats; and a handful of birds such as flamingoes and hornbills. There's also a display of mounted insects, and they run a regular free shuttle bus to the center of town.
It's open from 8:30am to 5:00pm, and admission costs ¥1000 for adults, ¥600 or ¥700 for students.