At Chankillo, the thing to look for is the line of thirteen towers on the ridge. They stand in a row along a low hill, each about two to six metres tall, spaced almost evenly like the teeth of a comb, and from a distance they look like a set of stone fingers. They date to the fourth or third century BC, and they are the key to the site's fame. Researchers have shown that if you stand at the right point on the plain, at one of two observation platforms, the rising or setting sun appears between the towers on different days of the year. At the solstices the sun rises at the two opposite ends of the row, and on days in between it rises behind a tower or a gap in the middle. The gaps between towers mark the calendar to within a day or two.
That makes Chankillo a working calendar, one that let ancient people track the seasons for planting, harvests and ritual. The two observation points are on either side of the towers, and each lines up with a different part of the horizon. It is a clear, simple system that works without instruments, and it is more than two thousand years old. UNESCO listed the complex in 2021, recognising it as the oldest known solar observatory in the Americas, and the claim has been published in major scientific journals.
A visit rewards patience. Walk first to the observation points and look toward the ridge, then climb the hill to stand among the towers. Dawn and sunset are the best moments for photographs and for understanding the idea, but at midday the light is flat and the heat intense. Take water and a hat. A small visitor centre has information and a local guide can explain the details. Wind blows constantly and carries sand.
The road leads through the desert coast, mostly on the Pan-American Highway, with long straights and a stiff crosswind. Casma, the main town nearby, has fuel and food, and the seafood is fresh. The dry season, from April to December, is the best time. Summer is hot and bright.