Cobá is one of the most important archaeological sites in the Yucatan Peninsula. Built between two lakes during the Classic Period (600-900 A.D.), it was at one time a very large city spread over 80 square kilometres. The main pyramid, Nohoch Mul meaning "large hill", is 42 metres tall (138 feet) and is the highest in the peninsula. It may not seem very high on this picture, but believe me, it's very steep and quite exhausting to climb. It's even harder going down...