Answer:
They're the birth place of Democracy.
Step-by-step explanation:
Ancient Greece was considered as the first civilizations that introduced the concept of Democracy.
The building in Ancient Greece was designed to accommodate a lot of audiences facing one specific direction where the speaker can present his/her case. The Roman civilization adopted this building and some principles from Greek's democracy.
American leaders in the past used these concept as a replacement for British' monarchy. They found that mimicking the building can be a source of inspiration that remind them about the core foundation of democratic government.