In Minecraft, an End Portal acts as a doorway. Inside that structure, you can have fire and liquid water as long as there are air blocks around it. This Minecraft tutorial explains how to make an End Portal with screenshots and step-by-step instructions. You can enclose soul sand or a magma block inside a completely closed structure in order for it to gradually fill the structure with air blocks, and any exposure or hole that is open to the biome will destroy those air blocks. Gravity will be one sixth the normal value, meaning that players and mobs will be able to jump 6 times as high as what they would be able in the overworld, and will resist falls six times as high.

Since there is no air, any kind of fire, incluiding torches and campfires will instantly extinguish, furnaces o smokers will not work, lava will explode like TNT, and water will either evaporate or become ice instantly, depending on which side of the moon you are on (bright or dark). The surface of the Moon would be bombarded by meteors small ones will cause small explosions (like those from ghasts) and big ones will act like TNT, but there is a chance they create random ore blocks after impact. Unlike designs that use horizontal pistons, the redstone here is completely hidden underground, and the door itself doesn't create an unsightly dip or gap in the wall. The frame must be made from andesite, with blocks of glowstone in the corners. This design is super simple and is the easiest invisible door that I've ever seen. Sounds will be attenuated, more opaque and quieter. The lunar portal is built using a frame, similar to the Photic Dimension. In that dimension, mobs and players will slowly drown as if they were on water, except if they have respiration or some breathing effect, similar but not the same as water breathing.

How to make portal to the moon