The archaeological site of Chichen Itza is located in the eastern portion of Yucatán state in Mexico. Chichen Itza was a large pre-Columbian city built by the Maya people. It was one of the largest Maya cities, with the densely clustered architecture of the site core covering an area of at least 5 square kilometres. The site contains many fine stone buildings in various states of preservation, and many have been restored. The buildings were connected by a dense network of paved causeways, called sacbeob. The Tzompantli structure or Wall of Skulls at Chichén Itzá is a Toltec structure, where the heads of sacrificial victims were placed. When visitors clap their hands in front of the 1,100-year-old Temple of Kukulcan, the pyramid answers in the voice of the sacred quetzal bird. Visitors must also watch their step as the site is covered in Iguanas.