Rotunda
A circular building is called a round building or a cylindrical building.
round room
Capitol records.
A building with a round roof, like the Capitol building in Washington DC or Saint Paul's cathedral in London.
Rondavel
Silo
A circular room in commercial buildings or out buildings is called a round house, in a private house it can be called among other things a turret. A rotunda is a round building or a room in a building, the central hall in the Capitol Building in Washington DC is an excellent example of a rotunda ( round room).
round pizza
Hearthome City, the round building.
The scientific name for round worms is "nematodes."
The name of Alaska's capital building is called the Federal and territorial building.