Fantasy environments, such as those above the clouds or in ridiculously beautiful places. I can think of one example, which would be the Titanfall map (I never know their names) with the large mac-cannonlike weapon aimed at an enemy ship. If you look in the background, you'll notice that the platform is above the clouds. I think that's pretty awesome. I also liked Blackreach, along with every other Dwemer construct across Skyrim and Morrowind. Ayleid structures were neat, but not as great.