Prefecture of Achaia has to present a wealth of buildings with unique architecture, influenced by different patterns of time. Characteristic are the buildings erected in the 19th and 20th centuries, and there is a set of industrial buildings that illustrate the economic and commercial development of the region during the 20th century. Equally important is the architecture of the mountainous villages of Achaia, which were built by Kloukiniotes-Varavarites craftsmen and are an important part of modern Greek folk architecture.

The architecture of Patras and Achaia in general, is clearly influenced by the various conquerors (Franks, Venetians, Romans, Byzantines) from antiquity to the present. The Roman Odeon 'most valuable throughout Greece after the Irodeio Odeon' according to Pausanias, the castle, the old Church of St. Andrew (1836 - 1843) testify the passing of centuries over the capital of Achaia.

The buildings that raise interest are in the center of Patras, the modern neoclassic buildings and arcades, with which the city was decorated in late 19th century and witness the prosperity of the city in that time. Ernest Ziller designed the neoclassical buildings that can be found in King George Square (central city) as the Municipal Theatre "Apollo" (1871) and the building of Commercial Association. Almost all the central streets of Patras, and the Upper Town is full of two-storey buildings (with paintings on the ceiling , frescoes and antefixes) as well as arcades and staircases. Of special architectural interest is the Catholic church of St Andrew and the Anglican church of Patras.
Of equal architectural value are the buildings of the city Aigio, with its private and public mansions and beauteous temples, holding a special place in Greek architecture.