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

Java Edition 21w20a – Minecraft Wiki

Snapshot 20W21A - Minecraft 1.16 Nether Update - Number 16! Custom

Java Edition 1.19 – Minecraft Wiki

Java Edition 22w16a – Minecraft Wiki

Nether Update – Minecraft Wiki

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CUSTOM Cave Dimensions & Redstone Has Changed. Again

Minecraft 1.16 Update

Datapack making

Java Edition 1.17 – Minecraft Wiki

Combat Update – Minecraft Wiki

Custom Dimension Minecraft Data Pack

Java Edition 1.19 – Minecraft Wiki