Spectacular rock formation along the Arakawa River in Nagatoro, Chichibu region. The Iwadatami are large, naturally flattened stone slabs shaped by erosion, resembling traditional tatami mats—hence the name. The site is designated a natural monument and is popular for scenic walks, river views, and traditional boat cruises known as linekudari. It's especially beautiful in autumn during the red foliage season, and in spring when the cherry blossoms bloom.

Price: Free access
Touristy? : Fairly touristy, especially on weekends and during peak seasons (spring/autumn).