The Decaying Kingdom

The only remains of a great kingdom that has sunken underneath the lava lakes, this structure spawns above the lava lakes in the nether (around Y level 32).

Champion's Graves

Found in the Taiga or Snowy Taiga biome in the overworld. This structure contains the haunted Old Champion's Remains, and perhaps you could even find some treasure left behind here...

Cathedral of Resurrection

Spawning in the Meadow or Plains biome in the overworld, the structure spawns with an Old Moon Altar block, which you can right click with a Lost Soul to summon The Returning Knight, or a Essence of Eventide to summon the Fallen Icon. It will contain loot.