The Grand Underground was introduced in Pokemon Brilliant Diamond and Shining Pearl, expanding the game and making it more exciting for players. You can dig and excavate treasures, as well as find Pokemon not available in the overground.
The Grand Underground is divided into 6 sections that can be accessed through different places in the overground Sinnoh Region. This ensures that players have to really work to find every area, every Pokemon, and complete the game. It certainly makes it all much more interesting! Find out where to access these sections below.
Accessing The Grand Underground
Before you access the Grand Underground, you will need to upgrade your Pokedex to a National Pokedex by visiting Professors Rowan and Oak in Sandgem town. You should then obtain an Explorer Kit from the Old Man in Eterna City. Three of the six sections can only be accessed with the Explorer Kit. Once you have your upgraded ‘dex and your kit, you will be ready to explore the Underground.
The Central Area: Inside this area, you can find Dazzling Cave, Stargleam Cavern, and Icy Cave. This small area can be accessed through Celestic Town.
Top-Left Area: This area contains Whiteout Cave, Dazzling Cave, Icy Cave, Spacious Cave, and Glacial Cavern. There are Ice type Pokemon hiding here! You can find this area by exiting Mt. Cornet as you go towards Snowpoint City. It is also accessible through Full Moon Island.
Bottom Left Area: This area contains Spacious Cave, Grassland Cave, Fountainspring Cave, Swampy Cave, Riverbank Cave, and Sunlit Cavern. You can find this area by digging near Twinleaf Town and some areas nearby.
Bottom Right Area: Here you can find Spacious Cave, Rocky Cave, Fountainspring Cave, Swampy Cave, Sandsear Cave, and Bogsunk Cavern. This area can be accessed by digging beneath Sunyshore City’s sunny shores!
Top Right Area: This area is the only area that serves as exclusive post-game content. Here you will find Volcanic Cave, Dazzling Cave, Sandsear Cave, Grassland Cave, Fountainspring Cave, Spacious Cave, Rocky Cave, and Typhlo Cavern. This area can only be accessed with the Explorer Kit, and only once you have completed the rest of the game. At this point, you should be ready to fight some pretty tough Pokemon!
The Main Area: This expansive area surrounds the Central Area and is so big it contains many areas, including Spacious Cave, Grassland Cave, Rocky Cave, Fountainspring Cave, Swampy Cave, Riverbank Cave, Volcanic Cave, Sansear Cave, Dazzling Cave, Big Bluff Cavern, and Still-Water Cavern. This area is so large that it is accessible nearly anywhere—particularly anywhere that has not already been mentioned!