Casma

In February 2008, German and Peruvian archeologists working at Sechin Bajo uncovered a stone and adobe ceremonial plaza which they dated to 5,500 years ago. This makes it the oldest known monument in Peru and one of the oldest structures ever found in the Americas.

The pyramid, main square, and circular sunken courtyard complexes extend over 1 kilometer (0.62 mi) in length.

The Thirteen Towers of Chankillo (Chanquillo) run north to south along a low ridge within a fourth-century BCE architectural complex in the Casma Valley, in northern coastal Peru.

From hypothesized observing positions within nearby buildings to the west and east, the towers form an artificial, toothed horizon that roughly spans the annual rising and setting arcs of the Sun. The Chankillo towers are interpreted as marking positions of the apparent annual solar movement along the horizon, and as evidencing Sun cults, preceding the Sun pillars of Cusco by almost two millennia.[3]

Las Aldas (or Las Haldas) is located on the Pacific coast, about 20 kilometers (12 mi) south of the Casma River and dates from 1800-1000 BC.

The lack of fresh water source nearby has led archaeologists to surmise that the people of Las Aldas traded seafood and other maritime resources for agricultural produce with the urban centers located inland, such as those of the Casma Valley and the Norte Chico civilization to the south.