An obelisk is a tall, four-sided, narrow tapering monument which ends in a pyramid-like shape or pyramidion at the top. Originally they were called tekhenu by their builders, the Ancient Egyptians. The Greeks who saw them used the Greek term 'obeliskos' to describe them, and this word passed into Latin and ultimately English. Ancient obelisks are monolithic; that is, they consist of a single stone. Most modern obelisks are made of several stones.