build a 1" thick hull out of steel in our desired shape,
fill it with the same gases at the same temperatures and pressures in Earth's atmosphere,
and let that baby loose on Venus.
I'm no aerodynamicist, but common sense tells me that the volume of your balloon city will have to be very large and the amount of 1" thick steel you need to bring from Earth will be so massive, most Mars colony proposals will seem lightweight in comparison. Might as well just go to Mars.