15th century Tibetan Hevajra mandala depicting the Buddhist deity Hevajra dancing with his consort Nairatmya at the intersection of four vajra gateways. This shows that they are at the centre of the cosmos. Skull symbolism is used in the mandala to show death and impermanence. Outide of the celestial palace are eight charnel grounds looked over by a mahasiddha (yogic master).