For life to prosper water is a fundamental necessity, but if so, how did the the ancient Maya build such a massive empire without a river to draw water from? This, the first of five videos from the BBC documentary Secrets of the Mayan Underworld, demonstrates how through a series of underground, water-filled caves that run under the majority of the Yucatan, the Mayan Underworld – contrary to their belief that it was a realm of spirits – was actually the life-source of the entire area....