Sacsayhuamán is an ancient Inca archaeological complex located in Cusco, Peru. It is famous for its impressive stone construction, which was part of the defensive walls surrounding the capital of the Inca Empire. The site is particularly known for its massive, precisely cut stones, some weighing over 100 tons, which fit together so tightly that not even a knife blade can be inserted between them.

Sacsayhuamán is considered one of the best examples of Inca engineering and stonework. It was constructed during the reign of Inca Emperor Pachacuti (mid-15th century) and later expanded by his successors. The exact purpose of the site is still debated, but it is generally believed to have served a ceremonial or religious function, as well as a military one.

The site includes a series of terraces, walls, and plazas, and it offers a panoramic view of the city of Cusco below. Sacsayhuamán is also a popular tourist destination and is associated with the annual Inti Raymi festival, a celebration of the sun god Inti.

The site is a UNESCO World Heritage Site, part of the broader historical area of Cusco.