Mount Tsukuba (筑波山 Tsukuba-san) is an 877 m (2,877 ft) mountain located near Tsukuba, Japan. It is one of the most famous mountains in Japan, particularly well-known for its double peaks, Nyotai-san 877 m (2,877 ft) and Nantai-san 871 m (2,858 ft). Many people climb the so-called "purple mountain" every year for the panoramic view of the Kantō plain from the summit. On clear days the Tōkyō skyline, Lake Kasumigaura and even Mount Fuji are visible from the mountain top. Most mountains in Japan are volcanic, but Mount Tsukuba is composed of non-volcanic rocks such as granite and gabbro. The area surrounding the mountain is known to produce beautiful granite, and many rock quarries still mine it today.