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 23w13a_or_b – Minecraft Wiki

Java Edition 1.9 – Minecraft Wiki

Java Edition 22w13oneBlockAtATime – Minecraft Wiki

Nether Update – Minecraft Wiki

Java Edition 20w14∞ – Minecraft Wiki

Java Edition 20w14∞ – Minecraft Wiki

Java Edition 1.18 – Minecraft Wiki

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

How to get Everything You'll Ever Need In a Minecraft Dimension

Java Edition 22w18a – Minecraft Wiki