Chankillo: The 13 Towers That Served as a Solar Calendar

Chankillo is a 2,300-year-old archaeological complex in the Casma Valley, about 15 km south of the city of Casma on Peru's northern coast. Its crowning feature, a line of thirteen stone towers along a desert ridge, formed the oldest known astronomical observatory in the Americas and was inscribed as a UNESCO World Heritage Site in July 2021.

Start with the towers. They sit on a ridge below the walled hilltop temple, spaced along roughly 300 meters of crest. From two fixed observation points — one east of the line, one west — the sun rises or sets in a different gap between towers on almost every day of the year. The system tracks the solstices with an error of only one or two days, which is how a pre-literate coastal society kept a ceremonial calendar without clocks or written records.

What You'll See at Chankillo

The site covers about 4 square kilometers of coastal desert, built from local stone and mud mortar. Two distinct areas reward your attention, and they feel quite different from each other.

The Thirteen Towers

The towers are low, square, and weathered — around 2 to 6 meters tall and 2 to 5 meters wide, with gaps of 4.5 to 5 meters between them. They won't look like much at first glance. The point is not the individual structures but the line they create against the horizon. Standing at the eastern observation point at dawn, you watch the sun break over one specific notch; come back a few weeks later and it breaks somewhere else. The easternmost tower marks the June solstice sunrise, the westernmost the December solstice. I found that knowing this in advance turned a row of rubble into something close to a working instrument.

Between the towers, archaeologists found pottery and offerings that suggest the gaps were used for ritual observances, not just practical timekeeping. Excavations in 2007 confirmed the observatory function with measurements taken from the two viewpoints, which are marked by small structures at either end of the line.

The Fortified Temple

A steep walk up from the towers brings you to the fortified hilltop temple, sometimes called the Fortaleza. Three concentric walls — some sources count more, as interior partitions have collapsed — ring the summit, pierced by narrow entrances. Original wooden lintels still sit above a few doorways, a small detail that struck me as remarkable given their age. The complex includes a central enclosure, small rooms, and storage areas, all clustered on a hill around 299 meters above sea level.

Most visitors underestimate the heat and the climb. Bring more water than you think you need, and wear shoes with tread — the desert gravel slides underfoot on the descent.

Planning Your Visit

Getting there takes some effort, and that effort keeps crowds low. When I visited at sunrise there was exactly one other person at the site.

How to Reach Chankillo

From Casma, drive south on the Panamericana Norte for about 12.5 miles (20 km), then turn left at the signed junction and follow the desert track to the site. The drive from Casma takes 30–40 minutes. The last stretch is sand and gravel: a 2WD car can manage it in dry conditions but may struggle after rain or in loose sand, and a dune buggy or high-clearance vehicle is the safer choice. No public transport runs to the site, so your options are a private car, a taxi arranged in Casma, or a guided tour. Tours from Casma cost from around US$43 for a combined Chankillo and Sechín day trip, and dedicated sunset tours run about 2 to 2.5 hours.

Opening Hours, Fees, and Access Rules

Entry is generally free, and the site is open during daylight hours, commonly 6:00 to 18:00, though government sources and visitor reports conflict on fees and hours. Check with the Casma tourist office before you go, and treat any quoted price as subject to change. The walk from the parking area to the main ruins takes around 45 minutes on a straightforward trail. Allow 2 to 3 hours for the whole visit — that includes the walk, the towers, and the temple climb.

A guide adds real value here. The site has almost no interpretive signage, and a local guide will show you the exact observation points and explain how the tower gaps map onto the calendar. Ask about English-language guides when booking in Casma; some tours run bilingual.

Best Time to Go

May through November is the dry season, with clearer skies and more comfortable temperatures. December through April brings the coastal garúa mist and higher humidity, though the site stays open year-round. For the astronomical payoff, aim for a solstice or equinox date — June 21 and December 21 are the key sunrises. Sunrise visits start around 4:30 a.m. from Casma to catch first light between 5:50 and 6:30, depending on the season. Late afternoon light on the towers is also excellent and far less punishing than midday.

The desert floor gets hot fast. April to November is the best window for combining Chankillo with nearby Sechín, another archaeological site about 5 km from Casma.

Respecting the Site

Stay on marked paths. The ground around the towers holds archaeological deposits, and the stone structures are fragile after 2,300 years of wind erosion. Climbing on the towers is not permitted, and there are no facilities on site — bring everything you need and carry out your trash.

Frequently Asked Questions

How long does it take to visit Chankillo?

Plan 2 to 3 hours on site, including the 45-minute walk from the parking area and the climb to the fortified temple. Add 30–40 minutes each way from Casma, so a half-day is realistic.

Is there an entrance fee?

Most official sources list entry as free, but reporting varies and local management can change the rules. Confirm current conditions at the Casma tourist office before setting out.

Can I visit without a tour?

Yes, with a private vehicle — the site is open during daylight hours and the trail is straightforward. Without a car, a guided tour from Casma is the practical option, since no public transport reaches the site.

When is the best time to see the solar alignment?

The June and December solstices are the marquee dates, when the sun rises behind the easternmost or westernmost tower. Any clear morning shows the calendar in action, though — the sunrise position shifts noticeably week to week.