The Roman Empire adopted Christianity and spread it throughout much of Europe. While this is one of the more important historical religious facts in the world, Roman society is famous for many things. Roads and building styles are two of the things Rome was famous for during the height of their civilization. Roman roads connected much of Europe. This made governing much easier for the Legions. It also allowed people an opportunity to travel further than ever before.
Romans legions were often kept busy during garrison duty. Because Rome sent her soldiers to all parts of their Empire, they needed barracks, baths and houses of worship. Rather than spend Roman money on local labor to erect these buildings, the soldiers built them. Standardized buildings were part of what Roman culture gave to the world. Where architectural advancements were not in place, many locals copied the Roman styles of building.
When the Roman Empire chose Christianity as its state religion, churches had to be built. Roman basilicas were often used as a template. A basilica has three halls off of a central area. Because this was a popular style with the Romans, it became part of the churches they built in their subject lands.