Sechin Alto

9.4667°S, 78.2833°W.

Sechín Alto in the Casma Valley, Áncash Region, Peru — the central platform pyramid of one of the oldest urban centres in the Americas, built between approximately 1600 and 1400 BCE during the Initial Period of Andean civilisation. Original base 300 by 250 metres; original height 44 metres on five terraces — at completion the largest stone monument in the western hemisphere. The pyramid was built of dressed granite blocks set in mud mortar and faced with polished white plaster, with the principal axis aligned to the rising sun on the December solstice. Sechín Alto predates the Chavín culture by approximately 700 years and is part of the larger Sechín Complex including Sechín Bajo and Cerro Sechín — the latter containing the famous frieze of more than 400 carved stone slabs depicting dismembered human warriors. Excavated since 1937 by Julio C. Tello, Donald Collier, and Peruvian missions.

The largest stone structure in the Americas at the time it was built, by a civilisation that predated every other documented Andean state by half a millennium.