Desert Hill

Desert Hill is one of the constituent Kingdoms of the Mushroom World, rule by Desert Hill's King. Much like the rest of the Mushroom World, it's typically a peaceful kingdom and has been a target of the Koopa Kingdom in the past.

Super Mario Bros 3.
Desert Hill was invaded by Bowser and the Koopa Troop during the events of Super Mario Bros. 3. Morton Koopa Jr. had been sent by Bowser to make mischief in the Kingdom as a part of Bowser's revenge plot after his defeat during the events of Super Mario Bros.. With a base of operations in his airship, Morton Koopa Jr. attacked Desert Hill on a stormy day and stole the King's Magic Wand, before transforming him into a Hoopster. The Koopa Troop quickly took over much of Desert Hill. Mario and Luigi, at the behest of Princess Peach, set out to save Desert Hill after saving Grass Land and its inhabitants. After making their way to Desert Hill Castle, Mario & Luigi boarded the Airship and defeated Morton Koopa Jr., before returning the Megic Wand to the King. Desert Hill was the second kingdom of the Mushroom World that Mario explored; after finishing there, Mario moved on to Sea Side.

Mario Kart DS
Much later, Mario and Luigi, along with their other opponents and many spectators, travelled to Desert Hill during part of the Mario Kart DS Grand Prix, where a racecourse built in a town called Desert Hills, served as the first course in the Flower Cup. During Mission Mode, the circuit was also used by Wario in Mission 2-6 and in mis[sion 4-4.