Dragonspiral Tower (Japanese: リュウラセンの塔Dragonspiral Tower) is an old tower where ZekromB or ReshiramW was sealed after the war thousands of years ago. It is first seen when N awakens the dragon inside for his plans. It is located in the western part of Unova, just above Icirrus City. Though it is not known who built it or when it was built, it is the oldest structure in Unova.
ZekromW or ReshiramB can be found here after the credits if the player had a full party and PC when prompted to catch them at N's Castle, because players are not forced to catch them under these circumstances. However, the game is programmed so that they will not be Shiny.