Causeway Forts
From Tolkien Gateway
The Causeway Forts were fortified twin towers, which made up the gate guarding the Causeway road from Osgiliath to Minas Tirith. At this point the road ran through the Rammas Echor into the Pelennor Fields.
During the War of the Ring, they were guarded by Faramir against the Witch-King but were easily overrun.
