Chicxulub crater, Yucatán Peninsula, Mexico

The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is located near the town of Chicxulub, after which the crater is named. It was formed by a large asteroid or comet about 11 to 81 kilometres in diameter, the Chicxulub impactor, striking the Earth. The date of the impact coincides precisely with the Cretaceous–Paleogene boundary, slightly less than 66 million years ago, and a widely accepted theory is that worldwide climate disruption from the event was the cause of the Cretaceous–Paleogene extinction event, a mass extinction in which 75% of plant and animal species on Earth became extinct, including all non-avian dinosaurs.
The crater is estimated to be 150 kilometres in diameter and 20 km in depth, well into the continental crust of the region of about 10–30 km depth. It is the second largest confirmed impact structure on Earth and the only one whose peak ring is intact and directly accessible for scientific research.
Source: Wikipedia