In architecture, an exedra is a semicircular recess, often crowned by a half-dome, which is usually set into a building's facade. The original Greek sense (a seat out of doors) was applied to a room that opened onto a stoa, ringed with curved high-backed stone benches, a suitable place for a philosophical conversation. An exedra may also be expressed by a curved break in a colonnade, perhaps with a semi-circular seat.
The free-standing exedra, often originally supporting bronze portrait statues is a familiar type of Hellenistic structure, characteristically sites along sacred ways or in open places in sanctuaries such as at Delos or Epidauros; sometimes Hellenistic exedras were built in relation to a city's agora, as at Priene.
Following precedents from Rome, exedrae continued to be in widespread use architecturally after the fall of Rome. In Byzantine architecture and Romanesque architecture this familiar feature developed into the Apse and is fully treated there. A famous use of the exedra is in Bramante's Belvedere extension of the Vatican palace.
In Muslim architecture, the exedra becomes a mihrab and invariably retains religious associations, wherever it is seen, even on the smallest scale, as a prayer niche.
Both Baroque and Neoclassical architecture used exedras. Baroque architects (for example, Cortona in his Villa Pigneto to enrich the play of light and shade and give rein to expressive volumes, Neoclassical architects to articulate the rhythmic pacing of a wall elevation. A classic example of a Baroque exedra on a (comparatively) reduced scale within its context, is the central niche of the Trevi Fountain (illus. at that entry) in Rome, sheltering a statue of Neptune.
The interior exedra was richly exploited by Scottish neoclassical architect Robert Adam and his followers. During the 18th century an exedra became a popular garden feature or folly, often used as an ornamental curved screening wall to hide another part the garden, examples can be found at Belton House and West Wycombe Park.
Many classicizing bandshells in public parks are exedrae, for the shape, with its half-dome heading, reflects sound forwards. The Hollywood Bowl's shell (illus. at that entry) takes the form of the head of a gargantuan exedra, stripped of classicizing details.