Historical beliefs · Documented tradition
Chankillo: thirteen towers that count the days
On a desert ridge in Peru's Casma Valley stand thirteen towers. From two observing points, the Sun rises or sets behind a different part of the line as the year goes on.
The record
- Who
- People of the Casma Valley in the Early Horizon period
- Where
- Casma Valley, north-central coast of Peru
- When
- in use about 250–200 BC
- Kind of evidence
- Archaeoastronomical site, inscribed on the World Heritage List in 2021 (UNESCO)
- A living tradition?
- No
A whole-year instrument
UNESCO describes the line of towers as spanning the entire annual solar rising and setting arcs, seen from two observation points, one still clearly visible. Unlike a single alignment on one solstice, it could mark the solstices, the equinoxes and every date between, to within one or two days.
Why it works
It works because the Sun's rising point really does walk along the horizon through the year, and turns back at the solstices. That drift is calculated for your own horizon on this site's Sun pages.
Sources
- UNESCO World Heritage Centre Chankillo Archaeoastronomical Complex (opens in a new tab) for 250–200 BC; thirteen towers span the year's sunrise and sunset arcs from two observing points; 1–2 day precision; inscribed 2021 · checked 2 October 2026
- Cool Moon Facts How the Sun pages calculate for the engine, its definitions, its independent checks and its limits