An obelisk (from Greek ὀβελίσκος - obeliskos, diminutive of ὀβελός - obelos, "spit, nail, pointed pillar") is a tall, four-sided, narrow tapering monument which ends in a pyramid-like shape at the top, and is said to resemble a petrified ray of the sun-disk. A pair of obelisks usually stood in front of a pylon. Ancient obelisks were often monolithic, whereas most modern obelisks are made of several stones and can have interior spaces.