An obelisk is a tall, four-sided structure with a pointed top, typically used as a monument or marker. There are several synonyms for obelisks, including monoliths, stelae, columns, pillars, and pinnacles. Monoliths are single blocks of stone or rock, while stelae are upright slabs or tablets. Columns are typically round or square and have a capital or decorative top. Pinnacles are also tall and pointed, though they can be natural formations or built structures. All these synonyms share the common characteristic of being tall and imposing structures, often used to mark significant locations or commemorate important events or people.