An obelisk (Greek ὀβελίσκος [obeliskos], iminutive of ὀβελός [obelos], "needle") is a tall, narrow, four-sided, tapering monument which ends in a pyramidal top. Ancient obelisks were made of a single piece of stone (a monolith); however, most modern obelisks are made of individual stones, and can even have interior spaces. The original form is Egyptian and all subsequent versions are derived from the original Egyptian pattern.