I’ve heard that Venus may be a better candidate, provided it can be cooled down and cleaned up.
From the plan i've heard, there is no need. They say the planet's atmosphere is so thick with Carbon dioxide, that larger containers would float on top of it. That just above the layer of Carbon dioxide is a massive layer of oxygen. That in this layer, the temperature is actually decent, like 70 degrees or so.
The idea is to make a large city held up in the sky by floating on the layer of carbon dioxide. The Idea has apparently been thought through quite a lot.
http://www.citylab.com/tech/2014/07/the-surprisingly-strong-case-for-colonizing-venus/373560/