<P> 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 Goombella and Professor Frankly , Mario learns that the map can potentially reveal the location of the seven 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 . </P>
where is the thousand year door in paper mario
in the ruins of the old town