I found this big lush cave while testing with mods, but confirmed that the seed works in vanilla too. The cave has an area of around 700×700 blocks. It's not very far away from spawn and easy to find as you can see a ton of trees in the desert close to the worldspawn. There are also several villages and two pyramids in the desert (pyramids at -470, -1190 and -790, -1430). I think I saw multiple trial chambers beneath the desert while flying in spectator mode too. I tested the seed on Bedrock but the cave doesn't generate there.
Version: 1.21.10
Seed: -1516680460343783540
Coordinates of desert with cave: -550, -1000
by gruen_ist_schoen