Ramanas Park
If you’re looking to catch Legendary Pokemon in BDSP, Ramanas Park offers the best way to do it. This area at the end of Route 221 (south of Sandgem Town) and is the holding ground for several postgame Legendary Pokemon, from Gen I to Gen III.

However, you’ll need to mine Mysterious Shards from the Grand Underground and exchange them for Slates to spawn the Legendary Pokemon.
Check out our Ramanas Park guide for more information on this area.
Catch Regigigas
The first Legendary Pokemon you can unlock in Ramanas Park is the trio of Legendary titans—Regice, Regirock, and Registeel. Capturing all three is the prerequisite to start the event of Regigigas inside the Snowpoint Temple.
Have all three of the trio in your party and head over to Snowpoint City. In the northernmost part of the city, you’ll find the temple in which only the “chosen one” may enter. The Snowpoint Temple has six floors, each with ice-sliding puzzles similar to the one inside the Snowpoint City Gym.
The very bottom floor is where you’ll find the statue of Regigigas. Save your game before interacting with it, as this will trigger the encounter with Regigigas.