Some similarities are that the buildings were very decorative outside, huge buildings, and the styles were similar. They were similar because the Romans partly inspired how Medieval Europe built buildings. They would use Roman ideas in their buildings. There were differences though. As time went on the technology available changed how things were built. People had better ideas, materials, and more noticeable buildings.
Monumental architecture is used to remember how these people built buildings. They show the new ideas brought by them. The Romans were the first to use basilica, arches, aqueducts, and residential housing block. The Roman colosseum is the biggest monument that they are known for. Some monumental architecture is very different. In medieval Europe they built castles and cathedrals. These buildings were very big and were used as churches sometimes. They were the first to use Gothic Architecture. This style uses stained glass windows, gargoyles, tall spires, turrets, and pointed arches.