The Roman Fort can be constructed on any of the following terrain and its (Hills) variant:
While functionally identical to a standard Fort, the Roman Fort can be built by a Legion rather than a Military Engineer. This means that the Romans have access to Forts as soon as they research Iron Working rather than Siege Tactics, effectively allowing them to start consolidating their defenses two eras earlier than other civilizations. By having their Legions build these in strategic locations around their territory, the Romans can make their lands virtually unassailable in the early stages of the game.
Civilopedia entry Edit
Since the first ego-maniacal chieftain threw up a wall of dirt and proclaimed everything behind it his, soldiers have been building fortifications. Whether to pacify new territory, protect the borders, or insure that the ruled didn't get uppity, the military-minded have dug ditches and moats, planted stakes and spikes, and put up walls of all sorts. Some made such military engineering an art form, such as the Roman legions, which could march through the day and have a fortified camp in place by nightfall. In time, the appearance of gunpowder led to innovations in fortifications; those wooden and stone walls were simply no longer adequate. So, rather than build up, fortifications went down – trenches and bunkers, pillboxes and minefields, barbed wire and "defense in depth." But the intent remains the same, to protect the troops and keep the civilization safe from both without and within.