At more than 90 bar, the lower atmosphere of Venus is basically made up of supercritical CO2, making it more or less a question of taste whether to call it an atmosphere or an ocean. Indeed, floating cities have been suggested as a way that man could actually live on the planet. High up in the atmosphere, the pressure and temperature would actually be quite livable.

And it could operate at the fringes of the Empire.

just small enough where the empire wouldn't bother...

relevant what-if

http://what-if.xkcd.com/30/

"The upshot is: Your plane would fly pretty well, except it would be on fire the whole time, and then it would stop flying, and then stop being a plane."

"A much better bet would be to fly above the clouds. While Venus’s surface is awful, its upper atmosphere is surprisingly Earthlike. 55 kilometers up, a human could survive with an oxygen mask and a protective wetsuit; the air is room temperature and the pressure is similar to that on Earth mountains. You need the wetsuit, though, to protect you from the sulfuric acid. (I’m not selling this well, am I?)"

>> But I've never seen the Icarus story as a lesson about the limitations of humans. I see it as a lesson about the limitations of wax

Oh brother, can't I vote for him ?