An exedra is a semicircular architectural recess or platform, sometimes crowned by a semi-dome, and either set into a building's façade or free-standing. The original Greek word ἐξέδρα was applied to
Exedra of Pamphilidas, Acropolis of Lindos, Rhodes, Greece
The foundations and partial floor of a late Roman villa. The floored part is the exedra. The rest of the floor has deteriorated and is missing, with only parts of the hypocaust columns remaining. Hot air circulated through the hypocaust to heat the house.
Exedra-shaped niche with a Apollo sculpture, at the Palazzo Giusti, Verona
Exedra of the Cortile della Pigna, at the Vatican Palace in Rome
In architecture, a niche is a recess or cavity constructed in the thickness of a wall for the reception of decorative objects such as statues, busts, urns, and vases. In Classical architecture example
Exedra
…architect Robert Adam and his followers. A classic example of a Baroque exedra on a (comparatively) reduced scale within its context, is the central niche of the Trevi Fountain in Rome, sheltering a statue of Neptune. Many classicizing bandshells in public parks are exedrae, for the shape, with its half-dome…
Niche with a sculpture by Antoine Coysevox, in the Les Invalides, Paris
Mihrab from the Mosque of Cordoba (niche shows the direction of prayer)
Porta Maggiore niches appear between arches.
Niches containing statues on exterior of Church of Orsanmichele, Florence, c. 1380–1404