The last royal pyramid was built around 1500 BCE. Afterward, while wealthy individuals were occasionally buried in or near pyramids, pharaohs were buried in the Valley of Kings, near Thebes (modern-day Luxor), the new capital of ancient Egypt. What exactly caused the rulers of Egypt to abandon the practice of pyramid burials is unknown, though many theories exist.One theory is that religious changes around 1500 BCE began emphasizing building tombs underground, in the bedrock, rather than interring bodies in pyramids. Thebes, unlike the previous Egyptian capital, Memphis, had far less open space and what little there was was rocky and rugged, hardly the ideal landscape to build massive monuments.

Tomb robbing was also an issue, and there was far less chance that burials would be looted if they weren’t placed in such conspicuous settings as horizon-dominating pyramids. The Valley of the Kings is a cliffy, complex landscape that was easy to hide royal burials and rock-cut tombs in. Tuthmosis, the first pharaoh to be buried in the Valley of Kings, hired a man named Ineni to inspect the excavation of his tomb. In his autobiography, Tuthmosis wrote, “I inspected the excavation of the cliff tomb of his Majesty alone, no one seeing, no one hearing.” Entrances were kept secret and necropolis guards patrolled the area for looters. more recent theory about why pyramid construction stopped comes from Peter James, an engineer tasked with examining the outer casing of the Bent Pyramid, built in 2600 BCE. While better preserved than other pyramids, which all have lost their outer casings of limestone and marble, the Bent Pyramid’s casing has also been breaking apart. Peter James discovered that the extreme temperature fluctuations of the Egyptian desert were causing the limestone to expand and contract, moving the stone blocks to the edges of the pyramid and forcing them to detach or break, taking the outer casing with them. Oddly enough, the Bent Pyramid’s unusual construction made it the best preserved pyramid; the gaps between the stone blocks have allowed them to shift with thermal expansion without breaking the casing. On the other hand, the more perfectly aligned and placed blocks of the Pyramids of Giza had no gaps between them. Any shifting of the blocks caused them to push against each other, causing the casing to disintegrate rapidly. This disintegration likely happened while pyramid building was still occurring. After spending so much time, money, and energy creating perfect monuments, this visible and rapid destruction of their perfection could have been one reason pharaohs abandoned them as burial monuments

The Great Pyramid of Giza is not only the most recognized of Egypt’s pyramids, it’s also the only of the Seven Wonders of the Ancient World that’s still standing. The Great Pyramid is impressive for many reasons, but one of the most interesting characteristics of this celebrated monument is that it can also tell time. The structure actually acts as an enormous sundial, with its shadow telling the hour by falling on marks made in the stone.

Of course, being the Great Pyramid, it couldn’t be just any old sundial. Its level of sophistication meant that it not only told time, but was able to signal solstices and equinoxes and therefore helped the Egyptians define the solar year.