To unlock Ramanas Park, which is south of Sandgem Town, you need to beat the Pokémon League and complete your Sinnoh Pokédex. (To complete the Sinnoh Pokédex, you don’t need to catch them all. You just need to see them all.) Once you do this, go back to Sandgem Town, and talk to Professor Rowan to get a special surprise visit from Professor Oak. Oak will talk about Ramanas Park, noting that you should go
