Round buildings with pillars are typically referred to as "rotundas." These architectural structures often feature a circular design and are supported by columns or pillars, creating an open and spacious interior. Rotundas can be found in various styles, from classical to modern, and are commonly used for public buildings, such as memorials, museums, or gazebos.
The Romans did not invent columns. They adopted the use of column to support the roofs of temples and for porticoes form the Greeks. They also adopted the three orders (styles) the Greeks used for columns: Doric, Ionic and Corinthian. They developed the Composite order which combined elements of two orders. The Egyptians used columns for their temples before the Greeks.
by using pillars
Rondavel
carve a square pillar :)
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).
The doors that go round and round are called revolving doors. They consist of multiple door panels arranged in a circular frame, allowing people to enter and exit buildings while minimizing air exchange. Revolving doors are commonly found in commercial buildings and hotels.
They are reinforced. :)
Haeting and cooling round buildings depends on the system and how it performs. Heating and cooling systems are not any easier to install in round buildings but are able to keep the environment cool or warm.
Romanesque Architecture
Norman architecture is also called "Romanesque" since it shares many features of Roman styles, including round arches supported by complete or half-pillars set against the walls each side. A typical Norman doorway has a number of pillars set at an angle to the plain of the doorway, supporting decorated tops from which the same number of recessed semicircular arches spring. These arches were typically decorated with carved zigzag patterns called "dogtooth". Originally Norman pillars and arches in churches and other important buildings were brightly painted but almost none of this paintwork survives. See links below for images:
colonnade
The use of pillars to hold up the roofs of facades of buildings, with three types - Ionic, Corinthian and Doric styles.