This pyramid, "the castle," is just one part of a large archaeological site that was a major city almost fifteen hundred years ago. It is believed that two groups of people, the Mayans and the Toltecs, called this city their home. The city included a marketplace, a plaza, a church, and an observatory, as well as a ball court, a temple for sacrifices, and a sinkhole which provided water for the people. The pyramid has four sides, each with ninety-one stairs; the four sets of stairs combine with the platform at the top to equal 365 three hundred sixty-five stairs-one for each day of the year. In addition, at sunrise and sunset on the spring and autumn equinoxes, the sun casts the shadow of a serpent moving down the pyramid toward the sinkhole. The observatory, used to study the sun, moon, and stars, provides further evidence of the Mayans' and Toltecs' interest in astronomy. Today this former city is one of the most popular in this south of the border country, seeing almost three million visitors each year. Where in the World
What is the name of this pyramid?