It honestly depends on what part of history you are referring to, but here are a few ways that the geography of Rome helped with its safety. Rome had an amazing navy, and the Romans designed thin, flexible boats that could maneuver around the islands and archipelagos and ram into the bigger ships of other countries. There were a few instances, during the Punic Wars, I believe, where the larger armies of other countries tried to attack Rome, but got stuck on the narrow paths. They could only send a few soldiers through at a time, and the Romans easily picked them off.
