The crane in the halfling slave camp before being retrieved.
The crane is an item you get after going through the halfling slave camp and freeing the people of Spree (then possibly killing them after doing so). Once you get this crane, reconstruction of the tower will begin, allowing you access to the Dark Tower Dungeons. Once you save the Red Hive, you will be able to retrieve the first smelter, which will open The Forge in the tower opposite the stairs to the spawning pit. When you save Rose in Spree Castle and return to the tower, the upper level, or Private Quarters, will also open, at which point the tower will be reconstructed.