According to Buddhist cosmology, Mount Meru (or Sumeru) is at the centre of the world and Jambūdvīpa is south of it. It is 80,000 yojanas wide and 80,000 yojanas high according to the Abhidharmakośabhāṣyam and 84,000 yojanas high according to the Long Āgama Sutra. Trāyastriṃśa is on its peak, where Śakra resides. The Sun and the Moon revolve around Mount Meru and as the Sun passes behind it, it becomes nighttime. The mountain has four faces, each one made of a different material—the Northern face is made of gold, the Eastern one is made of crystal, the Southern one is made of lapis lazuli, and the Western one is made of ruby.