arch, the
A curved structure, as a masonry, that covers openings in the stonework and is capable to supports the weight of material over an open space, as in a bridge, doorway, etc. It is often used as a decorative element.

architrave or epistyle
The lowest part of an entablature resting on the columns capitals and supporting the frieze.

drum
The cylindric parts of stone or marble, of which a column is built up.

entablature, the
The upper part of the classical order, that rests on the columns, it consists of the architrave, frieze and cornice.

hermaic stele, the
Column crowned with the bust of Hermes.

hippodamian plan
A town-planning system, developed by architect Hippodamus from Miletus. It was based on a grid-shaped plan which laid out roads and streets intersecting each other in opposite directions.

monopteros
A circular building with a single row of columns supporting a roof

peristyle
A colonnade surrounding a building or a courtyard .

pillar
Pier of square or rectangular cross-section.

Tetrarchs, the
The superior archons of the Roman state after its division in four parts by Diocletianus. The first group of Tetrarchs consisted of Diocletianus, Maximianus (Augusti), ο Galerius and Constantinus Chlorus (Caesars).