malthouses. Defence and escape The Poddle, and initially Dubh Linn too, naturally provided a water defence for the south and east faces of Dublin Castle, though its flow was not substantial enough to create a significant barrier, and a dam was built near the river's exit from the castle (giving the name to Dame Street), to provide a greater depth of water. A ditch was dug along the northern and western faces of the castle, and took some water from the Poddle, though the overall moat was at one time described as "partly wet and partly dry". The old town walls met with those of the castle at the Poddle, and a double arch was found in the northern part of the castle in modern times (the part where the moat passed under the town wall appears to have been filled in c. 1400). In 1592, Red Hugh O'Donnell and Art O'Neill escaped from Dublin Castle through a garderobe drain down into the Poddle, then proceeding out into the Liffey and on to the Dublin Mountains. This escape, O'Donnell's second, is commemorated by an annual trek from central Dublin into the mountains since five people began it in 1954; as of 2017, 200 hikers are chosen from 800 or more applicants each year. Flooding St Patrick's Cathedral and the Liberties The Poddle once flowed near what became St Patrick's Street in two streams, and the original St Patrick's Church was built between them and is recorded as Ecclesia S. Patricii in Insula (the Church of St Patrick on the Island). The church was elevated to collegiate status by John Comyn in 1191 and the early building of wood was remade in "hewn stone" and dedicated to "God, our Blessed Lady Mary and St Patrick" on 17 March of that year. The next prelate, Henri de Loundres, elevated it as St Patrick's Cathedral in 1213, which left Dublin as a rare city with two cathedrals. Historians have debated the choice of site, on marshy ground between two streams, and Bernard proposed that it could only be because of some holy association of the location, most probably with St Patrick. For centuries the Poddle, even as it was progressively culverted, caused regular flooding and dampness in the cathedral, as well as many other buildings in the Blackpitts and St Patrick's Street areas. On one occasion it is described as flooding the cathedral