The catchphrases "archaic simplicity" and "concentrating on the essentials" have taken hold in architecture, but these themes can also be explored on the scale of the city: How many different materials can a city take? At what point do vitality and variety give way to confusion and chaos? In the 20th century, attempts were made to create an identity for new communities with a homogeneous material. Examples include EUR's travertine surfaces in Rome (1930s), Chandigargh (1950s), and the terra cotta facades on Potsdamer Platz in Berlin (1990s). While these examples were all erected in a short period of time, there is a city in central Italy that evolved over the course of 2000 years in a single material. Since the days of the Roman Empire, Ascoli Piceno's bridges, towers, theatres, churches and palaces have been erected in the porous, calcareous stone. Piceno's travertine has a neutral colour and its texture can be either open-pored or dense. Owing to the stone's neutral surface, the entire city is transformed by changes in ambient light.
