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Sechin Bajo, Peru: The Location of the Oldest Man-Made Structure of the New World?

Sechin Bajo, Peru: The Location of the Oldest Man-Made Structure of the New World?

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Sechin Bajo is an archaeological site in Peru. This site is situated in the Casma Valley of Ancash, a region on the northwestern coast of that South American country. This site is believed to have served as the capital of a pre-Incan culture, and was occupied roughly between 1800 and 1900 BC.

More recently, archaeological excavations at the site have unearthed a circular stone plaza amidst its ruins. This has been regarded as a major discovery, since, based on initial analysis, the structure was dated to around 3500 BC. If this is true, this would indeed be a significant find, as it means that the plaza is the oldest man-made structure in the New World.

The Sechin Complex

Sechin Bajo is part of a larger archaeological area known as the Sechin Complex. The complex has been described as a “vast proto-urban settlement several miles in diameter”. The complex is believed to been centered around a mound called Sechin Alto, and, in addition to Sechin Bajo, includes the sites of Taukachi-Konkan and Cerro Sechin. Based on certain factors, such as the similarity in mound forms and site layout, as well as their orientation, it has been suggested that these sites were likely to have been part of a single, large, continuous settlement.

Map of the location of the Sechin Complex.

Map of the location of the Sechin Complex. (Nephicode)

Archaeological investigation of the Sechin Complex is recorded to have been carried out as early as the late 1930s. The ‘father of Peruvian archaeology’, Julio Tello, was the first archaeologist to survey the Sechin Complex, more precisely Sechin Alto. This is the largest monument in the Sechin Complex, and further investigations were carried out in Sechin Alto over the decades.

This monument has a U-shape plan, and covers an area of 200 hectares. The main mound has been measured to be 33 m (108.2 ft.) in height, and covers an area of 300 m by 250 m (984.2 x 820.2 ft.). Five plazas extend about 1.4 km (0.86 Miles) from this mound, three of which have sunken courts. It has been suggested that Sechin Alto was the largest monument in the New World during the 2nd millennium BC.

The layout of the Sechin Alto Monument Complex.

The layout of the Sechin Alto Monument Complex. (

Investigations at Sechin Bajo

As for the Sechin Bajo, archaeological investigation of this monument only began in 2000, though preliminary works had already taken place there in 1992. Sechin Bajo is situated on the northern edge of the Casma Valley, where the valley’s meadow merges with the desert. Covering an area of about 30 hectares, Sechin Bajo contains buildings from various periods of its occupation.

The site of Sechin Bajo.

The site of Sechin Bajo. (CC BY-SA 3.0)

Like Sechin Alto, the center of Sechin Bajo also was a mound. This mound, however, is smaller in size, measuring 18 m (59 ft.) in height, and covering an area of 180 m x 120 m (590.5 x 393.7 ft.) Excavations carried out on this mound have led to the suggestion that the mound was used for a variety of purposes over an extended period of time.

One of the important finds discovered at Sechin Bajo was a prehistoric relief frieze found on a temple wall. This frieze is made of clay mortar, and has been estimated to be between 3600 and 3800 years old. The figures on the frieze are characters depicted with various mythological / religious attributes, insignia, and weapons.

Another major find at Sechin Bajo was made in 2008. A circular plaza, which measures 14 m (45.9 ft.) in diameter, was discovered beneath the ruins of Sechin Bajo. This structure was found underneath another plaza that had already been discovered, and that it was rebuilt several times, perhaps once every century or three. It has been claimed that initial analysis has dated this structure to around 3500 BC, making it the oldest man-made structure in the New World.

Apart from the plaza, a 2 m (6.5 ft.) tall adobe frieze was also discovered during the excavation. This frieze is about 3600 years old, and depicts a man whose identity is debatable. On the one hand it has been suggested that the image portrays a human sacrifice, as he is interpreted to be holding a human head in one hand, and a ritual knife in the other. On the other hand, it has been suggested that the human head might have been a shield, and the knife, another sort of weapon. In any case, it is likely that the plaza served a ceremonial purpose.

A relief carving from the Casma/Sechin culture.

A relief carving from the Casma/Sechin culture. (CC BY-SA 3.0)

Featured image: Top Left: The newly found circular site at Sechin; Top Right: Walls encircling the site were uncovered; Bottom: The retaining wall of Cerro Sechin.  Source: Nephicode

By Wu Mingren


Hearn, K., 2008. Oldest Urban Site in the Americas Found, Experts Claim. [Online]
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JRB, 2012. Proyecto Arqueologico Sechín Bajo Casma, Peru. [Online]
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McDonnell, P. J., 2008. A new find is the Americas' oldest known urban site. [Online]
Available at:, 2016. The Sechin Complex: (Casma Valley Complex). [Online]
Available at:, 2008. Sechin Bajo. [Online]
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Wu Mingren (‘Dhwty’) has a Bachelor of Arts in Ancient History and Archaeology. Although his primary interest is in the ancient civilizations of the Near East, he is also interested in other geographical regions, as well as other time periods.... Read More

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