Cobblemon - Legendary

Hunt for legendary Pokémon throughout the world in these unqiue structures.
Each legendary is given a structure referencing it's in-game appearances, with unique loot to find in each structure.

Mysterious Mounds
Inspired by the Regi locations in Ruby, Sapphire and Emerald, these structures each contain one of five Regis.

Regice found in frigid Snowy Taigas
Regirock found in rocky Badlands
Registeel found in imposing Mountains
Regieleki found in the scorching Deserts
And finally, Regidrago in the mysterious Jungles

Snowpoint Temple
Hailing from the mighty Sinnoh region, Snowpoint Temple can be found in Snowy Taigas and is the resting place of Regigigas.
In this temple is a puzzle to solve in order to unlock the door to the bottom floor where Regigigas waits (Or you can drill through too if puzzles aren't your style.)
The temple also contains gilded chests with ancient loot inside, as well as, archeological spots if you've brought you're brush.

Dreamyard
The decrepit Dreamyard from Pokémon Black and White can be found in Forests.
Inside you will find one of the Eon Duo.
The rest of the ruins contains some more loot to find and Munna and Musharna also spawn here more commonly than other locations.

Suspicous Shed
This shed, which can be found in Plains, contains a Rotom.
While not a legendary, this Pokémon can still be a valuable team member, and you can pillage the shed for it's machinery too.