The Sphinx, the Great Pyramid of Giza, Cairo, Egypt.
Even with so few resources, they were able to build the Giza pyramids perfectly aligned with the Orion Belt. In addition, they are totally north-facing, with a very low margin of error.
The Sphinx that guards the pyramids of Giza does not have the nose. An ancient legend said that Napoleon and his soldiers had destroyed him. But more recent studies have shown that even before Napoleon the Sphinx no longer had a nose. And the mystery remains!