World 6-1 (Super Mario Bros. 2)

World 6-1 (Chapter 6-1 in Yume Kōjō: Doki Doki Panic; titled Go to the World of Deserts Again ) is the first level of World 6 in Super Mario Bros. 2.

Layout
This level starts like any level from World 2 does: as the desert is explored, numerous enemies and obstacles must be beaten, such as quicksand and swarms of Cobrats and Pokeys. Then a fort is entered, where 21 jars are seen. Only one of them has the key that is necessary to open the door showing Green Birdo's whereabouts. Another jar leads to a 1-Up Mushroom.

Trivia

 * Despite the Nintendo Power level title suggesting a direct revisit of the setting from World 2, it is stated that "World 6-1 looks a lot like the World of Deserts in World 2".
 * The correct jar is the fifth-to-last one.