Castles were built by the Anglo-Normans during the late 12th century, such as Dublin Castle and Kilkenny Castle, and the concept of the planned walled trading town was introduced, which gained legal status and several rights by grant of a Charter under Feudalism. These charters specifically governed the design of these towns. Two significant waves of planned town formation followed, the first being the 16th- and 17th-century plantation towns, which were used as a mechanism for the Tudor English kings to suppress local insurgency, followed by 18th-century landlord towns. Surviving Norman founded planned towns include Drogheda and Youghal; plantation towns include Portlaoise and Portarlington; well-preserved 18th-century planned towns include Westport and Ballinasloe. These episodes of planned settlement account for the majority of present-day towns throughout the country.