The Great Pyramid of Giza, which is the oldest of the Seven Ancient Wonders of the World and the only one to survive mostly intact.
Egyptologists believe that the pyramid was built as a tomb over a 10- to 20-year period concluding around 2560 BC. Initially, at 146.5 meters (481 feet), the Great Pyramid was the tallest man-made structure in the world for more than 3,800 years. Originally, the Great Pyramid was covered by limestone casing stones that formed a smooth outer surface; what is seen today is the underlying core structure. [source]
The Great Pyramid consists of an estimated 2.3 million blocks and it is estimated that 5.5 million tonnes of limestone, 8,000 tonnes of granite (imported from Aswan), and 500,000 tonnes of mortar were used in the construction of the Great Pyramid. [source]
Photograph via StugotzLobos on reddit
And a bonus video by Bright Side: