Shropshire Union Canal links are to the Llangollen Canal (at Hurleston Junction), the Middlewich Branch (at Barbridge Junction), which itself connects via the Wardle Canal with the Trent and Mersey Canal, and the River Dee (in Chester). With two connections to the Trent and Mersey (via the Middlewich Branch and the Staffordshire and Worcestershire Canal) the SU is part of an important circular and rural holiday route called the Four Counties Ring. The SU main line was the last trunk narrow canal route to be built in England. It was not completed until 1835 and was the last major civil engineering accomplishment of
Llangollen with Langolen in Brittany. Above the town to the north is Castell Dinas Brân, a stronghold of the Princes of Powys. Beyond the castle is the limestone escarpment known as the Eglwyseg Rocks. The outcrop continues north to World's End in Wrexham. The area nearest the castle is the Panorama Walk, and a monument to poet I.D. Hooson from the village of Rhosllannerchrugog can be found there. The ancient parish of Llangollen was divided into three "traeanau" ("traean" being the Welsh for "a third"): Llangollen Traean, Trefor Traean, and Glyn Traean. Valle Crucis Abbey was established at Llantysilio in about