The old Treasury buildings were first built in 1717. During restoration work carried out by the Office of Public Works in 1986, the massive lower section of the Gunpowder Tower, Dublin Castle’s 13th century north-eastern corner bastion, was discovered. As a result of preservation work visitors can now see underground the substantial base of the tower, steps leading up to a postern gate, a section of the old town wall, part of the Viking defensive embankment and the River Poddle itself. Visitors on the internal Dublin Castle tour are taken down to see these remains.