The Sixteen Realms

The Sixteen Realms are the worlds and dimensions parallel to Ninjago, which could formerly have been transferred via the Realm Crystal, an artifact that was located in the Tomb of the First Spinjitzu Master, but was destroyed by Flintlocke. Following the apparent destruction of the Cursed Realm after The Preeminent was destroyed, along with the destruction of Djinjago, there are currently only fourteen realms, including Ninjago.

Known Realms

 * Underworld
 * Ninjago
 * Digiverse
 * Cloud Kingdom
 * Dark Realm
 * Cursed Realm/The Preeminent (Now destroyed)
 * Djinjago (Destroyed due to the destruction of the Cursed Realm)
 * Chima

7 Other Unknown Realms

Realm Passageways
Each realm has it's own passageways: one from the Realm Crystal, and others such as the energy from the Golden Weapons combined, Traveler's Tea, the four Dragons, and Clouse's Book of Spells.

Trivia

 * The concept of the Sixteen Realms is similar to the Multiverse concept in various other fantasy and science fiction franchises. Notably, the fact that Chima is one of these worlds indicates that the Ninjago and Chima franchises share a Multiverse, though whether worlds based on other LEGO properties are also present is unknown.
 * Following their defeat at the hands of Captain Soto and his crew, the Sky Pirates were separated into various different realms, several if not most of which have not been featured or named in the series before.
 * Consequently destroying a realm could destroy its sister counterpart.