The Three Mountains of Dewa refer to Mount Gassan, Mount Haguro, and Mount Yudono, which resides roughly at the center of Yamagata Prefecture. The name Dewa refers to the name of the old province, current Yamagata and Akita Prefecture. The mountain range is a natural divider between the two major flat areas present in the prefecture: the Shōnai Region to the west and the Yamagata Basin to the east. The mountains have been deemed as a holy area to the religion of Shugendō and attracted many visitors for pilgrimage to the shrines located on their peaks and Japanese mountain ascetic hermits who practice the strict doctrine. Although the location attracts a considerable number of visitors, most of them are tourists who do not practice the Shugendō teachings. Mount Gassan is a stratovolcano and rises to the height of 1984 m. The area contains marshes and subalpine forests with many plants that grown in alpine meadows, including usagi-giku (arnica unalascensis), and rare animals such as ermine and alpine accentor. The renowned haiku poet Matsuo Bashō made a haiku at this site during his journey Oku no Hosomichi in 1689: