The second-largest moon in our solar system, Titan, orbits around Saturn, about 8.5 AU (the distance from Earth to the Sun) away from us, making it a very chilly place. A fairly massive moon (80% more massive than our moon, according to Wikipedia), it has the unique characteristic of having an atmosphere that obscured views of the surface until the launch of the Cassini-Huygens mission in 2004, designed to chart out primarily the Saturn system.
A moon with an atmosphere is strange, and interesting. But what makes Titan truly intriguing is the presence of a liquid cycle, akin to our water cycle, in it's atmosphere and on it's surface. An average temperature of -179.5 degrees Celsius means that this liquid isn't water - it's methane. The atmosphere and oceans of Titan are composed of liquid methane, which, under the conditions on the surface, acts similarly to water. It evaporates, precipitates, and forms liquid bodies and oceans, just like on Earth. Deeper down below the surface, there is, in fact, liquid water too, at higher temperatures and pressures beneath an icy "crust".
Titan is a strange planet, but interesting in it's composition. With a thicker, denser, and "taller" atmosphere than our own, it has some unique properties, and manages to be Earth-like in strange ways, by substituting life-giving water with a whole lot of poisonous (to us) hydrocarbons. But it is interesting nonetheless.