When we think about the underworld we usually imagine someplace dark, uncomfortable, scary, and full of bad things. Two days ago I picked up a book by a Kim Chernin (Re-Inventing Eve) and opened to this: "In Christian mythology no one wants to go down to the underworld." The Christian underworld image is Hell, a boiling hot cesspool that's home to the Devil. There are some variations---Dante describes the Inferno as cold and icy---but Hell is where all that is irredeemably bad ends up. Going to Hell is the ultimate, eternal mistake. Who would turn their ear to that ground, as Inanna does in her myth?
There are other views, other images from other times, cultures, and paradigms. The Sumerian underworld of Ereshkigal for example, is lifeless, dry, and therefore dusty. (They have no beer down there, which certainly fits my definition of hell). The Greeks sent their dead heroes and good people to the Islands of the Blessed and the Elysian Fields at the edge of the world. Underworld scenarios generally involve the dead, and this lifeless state is a form of exile. The dead aren't always gruesome or dangerous; they're often sad, bored, and privy to valuable information. Odysseus, for example, makes a sacrifice to the dead and is allowed to descend to meet them. He calls forth the spirit of the prophet Tiresias, who gives Odysseus advice about how to get back home to Ithaca safely.
The underworld as a psychological space is populated with folks (metaphorically) who are denied a place in the sunnier realms up top. They don't live as we do, among us. That population includes ideas, images, feelings, personal history or traits repressed or denied, consciously or unconsciously, for reasons that may no longer make sense. This burying process takes place collectively as well as individually. What you need may never surface unless you go down and get it, a key point in Chernin's discussion of the feminine in nature and the powers that the culture hides from us by virtue of our immersion in it.
How we imagine the underworld determines what we expect to find there and our willingness to go down. It has to be dark and deep and lonely---it's the underworld after all--- but sometimes the dragon living deep, deep down in the roots of the tree has a buried treasure of gold for anyone brave enough to stay the course. You might find your spontaneity, your poetry, your power, or your self-respect.