Peña de Bernal (in English: Bernal's Boulder or Bernal Peak) is a 433 m (1,421 ft) tall monolith, one of the tallest in the world.Peña de Bernal is located in San Sebastián Bernal, a small town in the Mexican state of Querétaro. The porphyrytic monolith was thought to have been formed 65 million years ago, during the Jurassic period. A recent chemical analysis by researchers at the National Autonomous University of Mexico has determined that it is considerably younger, likely formed about 8.7 million years ago.