Roundabout
Introduction
A circular or spherical temple, building, or room covered by a dome or roof is called rotunda.
They offer the shape of roundabouts:
The rotunda is also called the circular pavilion of pure ornament with a single row of columns "Column (architecture)") that was usually used in the gardens of the centuries and in imitation of the one in the gardens of Versailles with the name of Sala or Apollo grove.