There are all kinds of hotels in this world: There are luxurious hotels and expensive hotels. There are budget hotels and spa hotels. But there are also unconventional hotels that border on the absurd.

We're talking about hotels in igloos and hanging from trees. Hotels with themes that could quite possibly creep you out. But at the end of the day, all of these hotels have thrown conventional thinking out the window to create truly unique — and often awesome — experiences for their visitors.

After all, what's more memorable: a nice hotel with soft pillows, or one that requires you to hike up a mountain just to get in your bed? Memorability is key. And it's only achieved by properties that are one-of-a-kind, unique, kooky, and totally original. Here are 15 hotels that meet that criteria and then some.