<human>:  Why did archeologists stop digging up the pyramids in the early 20th century?
<bot>: The reason that archeologists stopped digging up the pyramids in the early 20th century is because they had already found everything of interest. The pyramids were built by the ancient Egyptians, and they were used as tombs for the pharaohs. The pyramids were built of limestone, and they were covered in a layer of sandstone. The sandstone was used to protect the limestone from the elements. The pyramids were built in the shape of a triangle, and they were made up of many layers of limestone. The pyramids were built over a period of many years, and they were built by many different people. The pyramids were built to last forever, and they were built to be a symbol of the ph