The Temple of the Night Sun used to be blood-red, making it visible for miles during dawn and dusk. It's decorated with 5-foot-tall stucco masks of the Mayan sun god that depict him changing as he travels across the sky over the course of the day.

From National Geographic:

The noonday sun is depicted as an ancient being with crossed eyes who drank blood, and a final series of masks resemble the local jaguars, which awake from their jungle slumbers at dusk.

Researchers found the first clues of the temple – high above what used to be the small Mayan kingdom of El Zotz – as they explored looters' tunnels near the 45-foot-tall Diablo Pyramid.

Archaeologists say that the temple was likely built between 350 and 400 AD to honor the founder of the first El Zotz dynasty known as Pa'Chan, or "fortified sky," who is buried under the Diablo Pyramid.

Mayan civilization, at its height between 250 and 900 AD, spread through southern Mexico, Guatemala, Honduras, El Salvador and Belize