It is filled with sand landmasses and at its end, where Snowglow Wood and a memorial could be found.
In its earliest recorded history, the tunnel was unfinished in the forms of dead ends and void openings. It also had a similar design to The Maze, but undoubtedly small.
During the Alpha Testing Stage, the tunnel could be swam into because the water did not damage the player. Images/videos of it during the stage were not recorded and/or reported.
On March 1st, 2018, the tunnel was finished in the form of sand landmasses, and the completion of the entire tunnel system. This led to players' speculation of an update relevant to an event, a new Wood Type, or a new item.
On March 13th, 2018, however, the biggest sand landmass held Snowglow Wood and a memorial for a very game-devoted player, Ticktatwert, who died of medical complications. The memorial was in a form of her YouTube thumbnail, a T, and a stone ramp that says "1997-2018".
You can get into the tunnel by driving any vehicle to sand slope and carefully don't let your health depleted.