 The game opens with an introduction about a seaside town which was damaged by a cataclysm and consequently sunk into the depths of the earth . A town named Rogueport was later built at this site , with the fortunes of the lost kingdom fabled to exist behind the eponymous Thousand @-@ Year Door , located in the ruins of the old town . Mario becomes involved when Princess Peach contacts him about a treasure map that she bought in Rogueport , but becomes part of a larger adventure after learning that Peach has gone missing . With the help of <unk> and Professor Frankly , Mario learns that the map can potentially reveal the location of the 7 legendary Crystal Stars , which are required to unlock the Thousand @-@ Year Door . Under the assumption that Peach herself is trying to find the Crystal Stars , he uses the map in an attempt to locate her . 
