Paramonga sits on a hill above the Fortaleza River, close to the town of Pativilca, several hours north of Lima on the Peruvian coast. It was built by the Chimú during the late Intermediate Period - roughly AD 1200 to 1400 - at the southern frontier of the Kingdom of Chimor, whose capital was the sprawling adobe metropolis of Chan Chan a few hundred kilometers farther north. Chimor controlled the northern coast of Peru for centuries, a loose confederation of walled cities and irrigated valleys that rivaled the Incas in engineering and succumbed to them only late, in the 1470s. Paramonga stood at the frontier - the last serious Chimú outpost before you hit the territory of Lima's central-coast cultures, including the oracle at Pachacamac whose priests held allegiances the Incas would later exploit.

The structure is often called a fortress. The word is imperfect. Paramonga is a staggered pyramid of four enormous levels rising on a natural hill, and what made it look like a medieval European castle to the Spaniards was an accident of converging building traditions - massive adobe walls, commanding elevation, defensible terraces - rather than any shared military theory. The Chimú almost certainly built it as something more than a fort. Its elaborate painted interior, the scale of its ceremonial platforms, and its proximity to the coast all suggest a religious complex on the order of Pachacamac itself. The original name is lost. The modern town of Paramonga gave the ruin its current label, and everything earlier is guesswork. What is clear is that the Chimú did not stack adobe like this for anyone less than their gods or their rulers, and that whoever commanded this place had access to skilled painters, master masons, and the labor to move thousands of cubic meters of earth by hand.

The conquistadors walked into this world in 1533. Francisco Pizarro had taken Atahualpa at Cajamarca the previous November, and the promised ransom of gold and silver was slowing to a trickle. The soldiers grew impatient. Atahualpa - captive but not yet desperate - offered Pachacamac, a coastal oracle held by priests who had backed his brother Huáscar in the civil war. Hernando Pizarro, Francisco's brother, took twenty horsemen and some arquebusiers, along with a handful of Atahualpa's own retainers as guides, and rode out along the Able Ñan - the imperial coastal road. Estete went with him. They became the first Europeans to sleep inside Paramonga. "A large town that is called Parmunga, which is next to the sea," Estete recorded, "has a Strong House, with five blind fences, painted elaborately on the inside and outside, with its walls carved the way it is done in Spain, with two tigers at the main entrance." The "tigers" were almost certainly pumas, painted guardians at the gateway of a complex the Spaniards had no conceptual vocabulary to describe.

Eight years later, in 1541, the chronicler Pedro Cieza de León passed Paramonga on his way from Lima to Trujillo. The paintings were still there. So were the ruins. "It is certainly very curious to see how they raised water in channels to irrigate higher levels," he wrote. "The buildings were very handsome, and many wild beasts and birds were painted on the walls, which are now all in ruins and undermined in many places by those who have searched for buried gold and silver. In these days the fortress only serves as a witness to that which has been." What had been was a Chimú civilization in the middle of being erased, with its painted walls gutted by treasure hunters within a decade of the conquest. The pumas are gone now. Most of the paint is gone. But the four stepped levels still rise above the Fortaleza River, visible from the Pan-American Highway, and on a clear day they still command the approach to a coast the Chimú once owned.