The original nucleus of the Roman colony of Salernum was a castrum, a military camp. The Roman castrums were not designed to withstand long sieges, as we are used to seeing in films about medieval castles with catapults, towers, fiery arrows, etc., but they had to prevent enemies militarily "
primitive" and militarily backward, armed with a sword, shield and ladder, penetrated inside the military camp. A series of ditches of medium depth, a boundary wall, made of wood or stone, was more than enough. But above all the Roman soldiers, once they identified the enemy, went to meet him, pushing him back into the open field.