An in-ground trampoline includes a plurality of walls designed to be connected together to act as a frame for the trampoline as well as act as a retaining wall for the hole the trampoline is located within. The walls are placed within the hole so a bounce mat of the trampoline is substantially flush with the ground. The walls receive springs that secure to the bounce mat and support the bounce mat at the appropriate height. The walls receive safety pads that will cover the upper edge of the walls and the springs for safety. The hole, interior to the walls, has a seepage pit formed therein for drainage. The hole may be deeper interior to the walls and the seepage pit may be located therewithin. The walls include lower platforms that extend outward and the lower platforms are backfilled over to provide support for the walls.