El Castillo, Chichen Itza

Technically, the clapping noise rings out and scatters against the temple's high and narrow limestone steps, producing a chirp-like tone that declines in frequency.

When a temple structure was renewed, the former construction was destroyed using a ritual that involved resolving the space of spiritual forces to preserve its sacredness.

During the 1930s restoration work, an entryway was cut into the balustrade of the northeastern exterior staircase to provide access to archaeologists, and later for tourists for the rest of the 20th century.

In 1924, the Carnegie Institution for Science in Washington, D.C. requested permission from the Mexican government to carry out explorations and restoration efforts in and around the area of Chichen Itza.

On June 7, 1932, a box with coral, obsidian, and turquoise encrusted objects was found alongside human remains, which are exhibited in the National Anthropology Museum in Mexico City.

[5] After extensive excavation work, in April 1935, a Chac Mool statue, with its nails, teeth, and eyes inlaid with mother of pearl was found inside the temple.

Inside this room, dubbed the "Chamber of Sacrifices", archaeologists found two parallel rows of human bone set into the back wall, as well as a red jaguar statue.

[6] The high status associated with the cinnabar pigment and its red tone suggest that the jaguar was linked to the ritual importance of closing a temple for renewal.

[6] The four fangs of the Red Jaguar have been identified as gastropod mollusk shells (Lobatus costatus) using a digital microscope and comparative analysis from malacology experts from the National Institute of Anthropology and History.

[5] The western and eastern sides of the temple are angled to the zenith sunset and nadir sunrise, which may correspond with other calendar events such as the start of the traditional planting and harvesting seasons.

[7] An approximate correspondence with the Sun's positions on its zenith and nadir passages is likely coincidental, however, because very few Mesoamerican orientations match these events and even for such cases, different explanations are much more likely.

[8] Since the sunrise and sunset dates recorded by solar orientations that prevail in Mesoamerican architecture, tend to be separated by multiples of 13 and 20 days (i.e. of basic periods of the calendrical system), and given their clustering in certain seasons of the year, it has been argued that the orientations allowed the use of observational calendars intended to facilitate a proper scheduling of agricultural and related ritual activities.

In agreement with this pattern, detected both in the Maya Lowlands [9] and elsewhere in Mesoamerica,[10] the north (and main) face of the temple of Kukulcán at Chichén Itzá has an azimuth of 111.72°, corresponding to sunsets on May 20 and July 24, separated by 65 and 300 days (multiples of 13 and 20).

[11] Around 2006, the National Institute of Anthropology and History (INAH), which manages the archaeological site of Chichen Itza, started closing monuments to the public.

Temple of Kukulcán before excavation, 1860
The Red Jaguar statue found in what is described as the throne room of the Temple of Kukulcán at the Chichen Itza archaeological site
Outlines of various pyramids overlaid on top of on another to show relative height
Comparison of approximate profiles of the El Castillo, Chichen Itza with some notable pyramidal or near-pyramidal buildings. Dotted lines indicate original heights, where data is available. In its SVG file , hover over a pyramid to highlight and click for its article.