Groundhog Castle is composed of an extensive range of tunnels underneath a spacious field where vegetables such as carrots are grown. When vegetables are not present, the field is open and bare, save for a few sparse trees and a large hole, and pockmarked with numerous smaller holes.
Nearly all of the castle appears to consist of neatly rounded tunnels just wide enough for a groundhog to pass through comfortably. There are at least two larger rooms: one in which the Bogwah is kept and Groundhog King's throne is located, and another, at the deepest reaches of the castle, where stolen vegetables were once kept.
The groundhogs once stole all of the vegetables growing above their castle after being convinced to do so by HighRoller. Commander ApeTrully of Big Green later came to investigate and was captured. First Squad came to his rescue, and were challenged by the groundhogs to a race through the castle's many tunnels, which was won by Jumpy Ghostface.