Grand Underground

The Grand Underground is an evolution of the Underground feature from Pokémon Diamnod & Pearl. It has been expanded to a larger area, segmented into 6 different areas which are accessed through various points in Sinnoh, based on your geography.

The best ways to get to each area is:

Access Map
Picture	Access Location	Areas
	Celestic Town	Dazzling Cave Icy Cave Stargleam Cavern
	Snowpoint City & Adjoining Routes/Full Moon Island	Whiteout Cave Icy Cave Dazzling Cave Spacious Cave Glacial Cavern
	Battle Zone	Volcanic Cave Dazzling Cave Sandsear Cave Grassland Cave Fountainspring Cave Spacious Cave Rocky Cave Typhlo Cavern
	Ramanas Park/Twinleaf Town/Canalave City & Adjoining Routes	Spacious Cave Grassland Cave Fountainspring Cave Swampy Cave Riverbank Cave Sunlit Cavern
	Sunyshore City & South east of Route 213	Spacious Cave Rocky Cave Fountainspring Cave Swampy Cave Sandsear Cave Bogsunk Cavern
	Everywhere else	Spacious Cave Grassland Cave Fountainspring Cave Rocky Cave Swampy Cave Riverbank Cave Volcanic Cave Sandsear Cave Dazzling Cave Still-Water Cavern Big Bluff Cavern

A new feature to this game is the Pokémon Hideaways. There's different biomes in each of the areas of the underground, and you can find wild Pokémon throughout the areas. Many Pokémon are exclusive to these Pokémon hideaways and more Pokémon appear at various points of your progression, with the National Pokédex being the feature that adds the most. Through this, nearly every Pokémon in the National Pokédex to Sinnoh

Secret Bases make a return in the Grand Underground. Here, you can use the Digging Drill item to create a Secret Base anywhere within the Grand Underground. When it is set up, people can visit your base. The base is decorated with statues that affect the spawns of the Pokémon in the various hideaways.

Click here for full mechanic details

Click here for full Statue & Hideaway manipulation details