The architecture in all three thief games was inspired by many historical periods. Old medieval castles coexist with newer Victorian or classicist buildings. Some old buildings were 'improved' with steam punk gadgets or feature a metal cladding, like the outer walls of the Shoalsgate Station. It is notable, that most stone made buildings in the City have flat roofs, while timbered houses usually have normal roofs. Styles also differ between the poor areas and the more prosperous ones and additionally there are differences between the games.
For an unknown reason, the architecture between T1 and 2 is radically different from T3. Ordered, organized bricks and cornerstones take over from the piles of cobblestone, iron frames and red brick. Thief 2 holds many architectural styles of the Industrial Revolution, with brick, iron frames, and greenhouses. In Thief 3, these styles are replaced by High Medieval-style buildings, with much more rustic designs.
The majority of the Dark Project buildings are solid stone, some with stone merlons. Few exotic buildings like Constantine's Mansion or the Ramirez Manor. Interior of the Opera House is mostly baroque.
Much like T1 but more classicist buildings and more Victorian interior. Many more Industrial Age pieces, such as metal frames and metal plates.
More timbered houses with ogive windows. Very few Victorian and no classicist buildings. In the Docks, the buildings show extreme 'jettying", or leaning out as they go higher.