They just added New Dimensions to Minecraft (1.16 Snapshot Update 20w21a)

Here's a look at the NEW custom dimensions added to Minecraft 1.16. You can now add your own custom worlds and dimensions! This is awesome!PLAY Block Ness Mo

Nether Update – Minecraft Wiki

Java Edition 1.20.3 – Minecraft Wiki

Java Edition 1.16 – Minecraft Wiki

Minecraft 1.16 Snapshot 20w21a Custom Dimension & Custom World

Nether Update – Minecraft Wiki

Minecraft 1.16 Nether Update Answers! Aether Dimension, New Biomes

New Dimensions in Minecraft???, Snapshot 20w14infinite

Minecraft 1.16 Update

Minecraft 1.16 Update Mod (snapshot 20w18a Update!) - Modding