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
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
In architecture, an alcove is a small recessed section of a room or an arched opening. The section is partially enclosed by such vertical elements as walls, pillars, and balustrades.
Niche (architecture)
…an aedicula on Lake Albano in Italy has six niches of varying heights, suggesting that anything up to the height of the statue could be accommodated. Alcove (architecture) Grotto…
A semi-dome surmounting an alcove in the Villa Ephrussi de Rothschild