You are likely thinking of Shirakawago and Gokayama, both of which are UNESCO World Heritage Sites, and contain many homes constructed in the gassho-zukuri style (A-frame).

Japan has 18 world heritage sites; 14 cultural and 4 natural.

The cultural sites are:

- Buddhist Monuments in the Horyu-ji Area

- Fujisan, sacred place and source of artistic inspiration

- Gusuku sites and Related Properties of the Kingdom of Ryukyu

- Himeji-jo

- Hiraizumi - Temples, Gardens and Archaeological sites representing the Buddhist Pure Land

- Hiroshima Peace Memorial (Genbaku Dome)

- Historic Monuments of Ancient Kyoto (Kyoto, Uji, and Otsu cities)

- Historic Monuments of Ancient Nara

- Historic Villages of Shirakawa-go and Gokayama

- Itsukushima Shinto Shrine

- Iwami Ginzan Silver mine and its Cultural Landscape

- Sacred Sites and Pilgrimmage Routes in the Kii Mountain Range

- Shrines and Temples of Nikko

- Tomioka Silk Mill and Related Sites

The natural sites are:

- Ogasawara Islands

- Shirakami-Sanchi

- Shiretoko

- Yakushima