Loompaland is the place where the Oompa-Loompas come from.
According to Willy Wonka himself, the whole place is nothing but thick jungles, desolate wastes and the most horrid beasts in the world; Hornsnozzlers, Snozzwangers, Vermicious Knids and Whangdoodles (beasts that, unfortunately, were never documented). The island itself isn't documented either (not even on a map or computer system), and as a result most people outside of Wonka's circles dismiss it as nonsense.
The Oompa-Loompas used to live in tree houses to escape the monsters, where they ate green caterpillars, which, also according to Wonka, tasted revolting. He also learned that the Oompa-Loompas craved cocoa beans, so Wonka offered them to work and live in his chocolate factory, and they could have all the cocoa beans they wanted.