No less than 109 ancient caves stand majestically in Mumbai's backyard, Sanjay Gandhi National Park. They are more than 2400 years old and are known for being one of the country's oldest and largest cave formations in a single hill. Kanheri saw activity for about an entire millennium (1st century BC to 11th century AD). Inscriptions refer to it as Krishnagiri, meaning 'black mountain' since it is made of black basalt stone. Imagine the time taken to hand-chisel the caves themselves, let alone their elaborate sculptures!