Gilbert Hill is a 200 ft (61 m) monolith column of black basalt rock at Andheri, in Mumbai, India. The rock has a sheer vertical face and was formed when molten lava was squeezed out of the Earth's clefts during the Mesozoic Era about 66 million years ago. During that era, molten lava had spread around most of the Indian states of Maharashtra, Gujarat and Madhya Pradesh, covering an area of 50,000 square kilometres (19,000 sq mi).