Underground

The Underground is an area deep under the earths of your Terrarian world. Most spawn points seem to be at +100ft. Digging down will bring you to a dirt layer (below the surface yet still above +0ft), but until you breach the -0ft layer (which is marked with rocks in the dirt background) you will not technically be underground. You will know you are in the Underground area when you hear the daytime/nighttime music change to a completely different song (not to be confused with the Cavern Layer). In the Underground area, you can find random Crystal Hearts that can only be harvested with a hammer as well as chests containing loot, such as the Hermes Boots. Underground is the best place for beginners to venture in.

From time to time, you may bump in to a mud field full of Glowing Mushrooms. Tall glowing mushrooms must be cut down with an axe like a tree, while the smaller glowing mushrooms can be cut down with any weapon/tool. Cutting down the tall glowing mushrooms occasionally drops Mushroom Grass Seeds which can be planted in order to grow a Glowing Mushroom field.