The R357 road from Ballinasloe, Co. Galway to Cloghan, Co. Offaly crosses the River Shannon at Shannonbridge on the sixteen-arch masonry road bridge completed in 1757. Before the bridge approaches on the western side of the river the road runs through the Tete-de-pont or bridge defences which were constructed during the Napoleonic Wars.
Google Earth view of the Shannonbridge artillery fort showing the main redoubt with the ramp in front of it, the Ballinasloe road running along side it entering the fort just in front of the fortified Barrack Block.
The defences were designed to delay a military force apparoaching from the west from crossing the River Shannon to the eastern side. The defences take the form of an elongated triangle with blunted western end, consisting of a sub-rectangular redoubt in front of a wedge-shaped enclosure and connected to it with a pair of diverging stone walls. The redoubt was completed in 1810, the barack Block in 1814 and the rest of the defences in 1817. This was at the same time as the reconstruction of Athlone Castle. The bridgehead fortification is of great historic significance and is thought to be unique within Ireland and Britain. The site is a Recorded Monument No. RO056-016--- but has been highligted on the National Monuments Service Map Viewer for delisting from the Record.
View of the Shannonbridge artillery fort barrack block from the Ballinasloe road. Three guns situated on the roof of the building.
The western artillery redoubt has a glacis slope and dry moat faced in stone on all sides. It is on a rise overlooking the road and had 4 guns on traversing platforms. To the west in front of the redoubt the ground has been cleared and turned into a ramp sloping toward the redoubt, providing the artillery with a designed killing zone. The redoubt is connected to the rest of the fort with high stone walls, that are glacis or sloping to the north. The enclosure to the east is wedge-shaped with the widest part resting on the river bank. On the southern side is a fortified Barrack Block with emplacements for 3 guns on the roof that had a field of fire directly down the Ballinasloe road. In front of the Barrack Block the road turns north though what was a gated entrance into the fort and the approaches to the bridge. On the north flank of the fortifications was a small arms battery for musketry defence, symmetrical with the barrack block. The barrack block is now in use as a restaurant.
The Tete-de-pont was supported with additional fortified batteries situated on Lamb Island in the river behind it and on the eastern bank of the river south of the bridge.
Google maps image of the location of Shannonbridge artillery fort.