[Futaba-chan]

Spoiler for episode 17:

The Ruins look like an impact crater! So, were they formed by A) an existing city or temple being bombed by a nuclear or antimatter weapon or a large meteorite, B) the crash of a colony ship, C) something enormous teleporting in, D) something enormous teleporting out (think Super Dimension Fortress Macross), or E) a meteorite landing in the middle of nowhere, which later happened to be a convenient site for building a pueblo-style settlement?

For that matter, the harbour and spiral-shaped promontory where the Grand Temple is located looks an awful lot like another (flooded) impact crater....