Noun
a round arch drawn from a single center
Source: WordNetHe designed the façade of Saint-Denis to be an echo of the Roman Arch of Constantine with its three-part division and three large portals to ease the problem of congestion. Source: Internet
Roman Arch of Marcus Aurelius In spite of centuries of Roman habitation, the only visible Roman remains, apart from scattered columns and capitals (usually integrated in later buildings), is the Arch of Marcus Aurelius from the 2nd century AD. Source: Internet