Buried Spawner Dungeons in Desert Biomes

When you're crossing a desert biome, you'll often come across curiously regular features.

Looks can be deceiving!

Rectangular holes are one example that are really worth investigating.

Another example of a buried spawner dungeon in the desert.

They form when the seed is created, and a spawner room has a sand ceiling that collapses.

Buried spider spawner dungeon after the sand is removed

They'll usually have chests, too.

This buried zombie spawner dungeon also has an entrance to caves

Here's a link to seeds we've found with hidden desert spawner dungeons.