Although no longer the de facto city centre, Medieval Dublin is the true heart of Dublin. It was here that the first settlements were constructed by the Norse around the year 841. Many of the buildings constructed by the Vikings and Norse are still standing today, albeit in rebuilt form. These include Dublin Castle, Christchurch Cathedral and St. Patrick's Cathedral. The Dublinia heritage centre located near Christchurch Cathedral is a fascinating source of information about the area in medieval times.