Castamere is the Downworlder home country, a sanctuary hidden from mundanes, given to them by the Demon Illyria. Its capital, and only city, is Illyria, commonly referred to as Illyria’s Landing. The country is said to be surrounded by mountains and giant bodies of water which must safely be traversed with the company of Shadowhunters, given the dangerous population.
Most Downworlders come from outside of Illyria, but many of them do at some point visit Castamere, very few stay. Castamere is located in Central Europe, between present day Switzerland, France and Spain. Because of wardings placed around the country and all of its borders, mundanes who come close to crossing it are instantly transported through to the other side of the barrier. Only mundanes that possess The Site can enter. There are also a few establishments in Castamere as well as a few towns.