Aria: The Natural: Tooi Yume no Mirage

Aqua and Aria take place in the early 24th century, starting in 2301 AD, in the city of Neo-Venezia on the planet Aqua - formerly Mars, which was renamed after being terraformed into a habitable planet covered in oceans around 150 years beforehand. Neo-Venezia, based on Venice in both architecture and atmosphere, is a harbor city of narrow canals instead of streets, traveled by unmotorized gondolas.