Volcanoes, stay away from the core, or not…
Siege castles to get settlements for your travels! Look for them in plains.
Assault pirate ships
The mod comes with little ships templates, a big galeon and a treasure island.
Strongholds, try to find the entrances at taiga biomes.
And thats supposed to be under the towers:
Swamp caves are very big, and with some flowers!!
Nether cities (Caution, secret rooms inside)
If you see a pyramid(or something suspicious in deserts), go in, look for the trapdoor in the maze and jump in to fight the boss:
Look for this caves in wet biomes to find the slime boss:
Nether holes, you will see red sky, also removed bedrock from top.
A default dungeon (In the download version dungeons will be at layers 18-60, this was just for testing)
A big one (size configurable in properties, look top)