Complex sentence: During the period 2011-2013 the castle underwent a massive redevelopment, with €5.7m being spent to improve the visitor facilities of the castle the redevelopment was completed by the same people who did the Titanic Exhibition in Northern Ireland.
Split into simpler sentences: During the period 2011-2013 the castle underwent a massive redevelopment, with €5.7m being spent to improve the visitor facilities of the castle. The redevelopment was completed by the same people who did the Titanic Exhibition in Northern Ireland.