sentences:  Segments of the town wall are still visible in various parts of the town and in various states of preservation.Archaeological excavations close to the walls' foundations have yielded many artefacts that have helped historians piece together a picture of the lives of the 12th and 13th century inhabitants.Carrickfergus became an inhabited town shortly after 1170, when Anglo-Norman knight John de Courcy invaded Ulster, established his headquarters in the area and built Carrickfergus Castle on the "rock of Fergus" in 1177.