This page outlines how to enter the Grand Underground.
The Grand Underground is a massive labyrinth located deep underneath Sinnoh. In the original Diamond and Pearl, it was simply known as the “Underground”. Here, you can freely explore, dig up useful items, set up a base or even find rare Pokémon.
To access the Grand Underground, you must first obtain the Explorer Kit.
Where is the Explorer Kit?
You can get the Explorer Kit from Eterna City, via the house to the right of the Pokémon Center. The Explorer Kit will be stored in the Key Items section of your bag. Using the kit, you can instantly travel to the Grand Underground from almost anywhere.
The location where you use the kit will determine where you begin in the Grand Underground. However, the reverse is not true; using the Explorer Kit again will always return you to your original location, no matter where in the Grand Underground you are.
While in the Grand Underground, you can partake in the following:
Dotted around are various large rooms (indicated by a question mark on the map) that contain miniature environments, such as volcanic landscapes. These are called Pokémon Hideaways.
Unlike your adventures above ground, you can physically see the wild Pokémon, similar to Pokémon Sword and Shield. Also, the Pokémon that you can encounter include those not normally found in the Sinnoh region.
Dig for Treasure
Certain walls can be inspected. A puzzle screen will appear, where you can use a sledgehammer and pickax to dig away at the wall, potentially revealing valuable treasure. However, there’s a limit to how many times you can dig, before the wall collapses and you’re forced to leave.
- The Sledgehammer clears away a wider area of rocks, but will cause the wall to collapse more.
- Meanwhile, the Pickax works on a smaller area, but will cause less damage to the wall.
It’s a good idea to start with the Sledgehammer, then swap over to the Pickax to focus on a specific area. You can swap tools by pressing the R button or tapping the touch screen.
To obtain a treasure, you must fully uncover it–in other words, it’s completely visible, with no rocks obscuring it. Once you’ve recovered all the treasure or the wall reaches its limit, you’ll receive all the treasure you recovered.
You can use the Digger Drill on a wall to create an entrance to your own Secret Base. Inside your base, you can place Pokémon statues, which can alter the species of Pokémon that appear in Hideaways.
It’s possible to explore the Grand Underground with other players via Local or Online communications. Each player will need their own Nintendo Switch and copy of Brilliant Diamond or Shining Pearl. Also, for Online play, each player must have an active Nintendo Switch Online subscription.