Carlow Castle was constructed by William Marshal, Earl of Striguil and Lord of Leinster, c1207-13, to guard the vital river crossing. It was also to serve as the capital of the Lordship of Ireland from 1361 until 1374. This imposing structure survived largely intact until 1814 when it was mostly destroyed in an attempt to turn the building into a lunatic asylum. The present remains now are the West Wall with two of its cylindrical towers. The bridge over the river Barrow – Graiguecullen Bridge, is agreed to date to 1569. The original structure was largely replaced and widened in 1815 when it was named Wellington Bridge in celebration of the defeat of Napoleon's army by the Duke of Wellington at the Battle of Waterloo in June of that year. The bridge was built across a small island in the river and a 19th-century house was constructed on the bridge – this was for a time occupied by the Poor Clares, an enclosed religious order who still have a convent in Graiguecullen. Another convent belonging to the Presentation Order of nuns now houses the County Library and the Carlow County Museum. The Cathedral, designed by Thomas Cobden, was the first Catholic cathedral to be built in Ireland after Catholic Emancipation in 1829. Its construction cost £9,000 and was completed in 1833. Beside the cathedral, Saint Patrick's College dates from 1793. The College was established in 1782 to teach the humanities to both lay students and those studying for the priesthood. The Carlow Courthouse was constructed in the 19th century. There are still many old estates and houses in the surrounding areas, among them Ducketts Grove and Dunleckney Manor. St Mullin's today houses a heritage centre.