 If you liked
So Ra No Wo To
|
 ...then you might like
Suisei no Gargantia
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So Ra No Wo To and Suisei no Gargantia both feature lots of world-building, strong art direction and designs (the primitive "Yunboros" of Gargantia are especially great), and an initially lighthearted atmosphere with more serious undertones. Unfortunately, many of the tone shifts in each series could have been better executed as both sometimes suffer from what I like to call "AIJOU YUUJOU syndrome." You'll see where that names comes from if you watch some of the more sombre episodes of So Ra No Wo To.
All that said, if you enjoyed one of these, you should strongly consider watching the other.