rotunda

a large circular room

a round hall or building that often has a rounded roof as well

A rotunda is a round, often domed building or room, typically with a circular floor plan. It is usually open and spacious, with a high, vaulted ceiling that may be supported by columns or arches. Rotundas are often used for public buildings, such as museums, government offices, or halls, and are designed to create a sense of grandeur and openness. The central, open space of a rotunda often serves as the focal point of the building, with surrounding rooms or hallways branching off from it. Rotundas can be found in both classical and modern architecture.