A flying buttress is not a feature of Romanesque architecture.
Round arches
Flying buttress
stained glass
Roman
Barrell vaults
During the medieval period the main style of architecture was Gothic.
The Romanesque style of cathedral-building spread throughout western Europe during the eleventh century and half of the twelfth century... Page 327, The west encounters and transformations
stained glass
Julius Baum has written: 'Romanesque architecture in France' -- subject(s): Architecture, Architecture, Romanesque, Church architecture, Romanesque Architecture
Alfred William Clapham has written: 'English romanesque architecture before the conquest' -- subject(s): Church architecture, Cross and crosses, Crosses, Romanesque Architecture 'English romanesque architecture' -- subject(s): Church architecture, Crosses, England, Romanesque Architecture 'Romanesque architecture in England' -- subject(s): Architecture, Romanesque Architecture 'Thornton Abbey, Lincolnshire' -- subject(s): Thornton Abbey
The Hagia Sophia is not romanesque architecture. It is byzantium.
romanesque.Medieval architecture is actually referred to as Gothic Architecture.
Harald Busch has written: 'Pre-Romanesque art' -- subject(s): Architecture, Romanesque, Art, Romanesque, Romanesque Architecture, Romanesque Art 'Renaissance sculpture'
Godehard has written: 'Rheinische Romanik im 19. Jahrhundert' -- subject(s): Architecture and state, Architecture, Romanesque, Church architecture, Conservation and restoration, Romanesque Architecture, Romanesque revival (Architecture)
Thomas Inkersley has written: 'An inquiry into the chronological succession of the styles of romanesque and pointedarchitecture in France' -- subject(s): Architecture, France, Architecture, Gothic, Architecture, Romanesque, France Architecture, Gothic Architecture, Romanesque Architecture
Felix Kayser has written: 'Kreuz und Rune' -- subject- s -: Architecture, Romanesque, Art, Romanesque, Lombards, Romanesque Architecture, Romanesque Art
Jean-Maurice Rouquette has written: 'Provence romane' -- subject(s): Architecture, Romanesque, Church architecture, Romanesque Architecture
Raymond Oursel has written: 'Airvault' -- subject(s): Saint-Pierre d'Airvault (Church) 'France romane' -- subject(s): Architectural Decoration and ornament, Architecture, Romanesque, Church architecture, Decoration and ornament, Architectural, Romanesque Architecture 'Lyonnais, Dombes, Bugey et Savoie romans' -- subject(s): Art, Romanesque, Romanesque Art 'La dispute et la grace' 'Haut-Poitou roman' -- subject(s): Architecture, Romanesque, Church architecture, Romanesque Architecture 'Romanisches Burgund'
Because the Romanesque architecture combines elements of older Roman (think ancient Rome) and Byzantine architecture. Mostly this type of architecture was prevalent during the Dark Ages in Europe, which came after the fall of the Roman empire.