Researchers at NASA's Langley facility developed the High Altitude Venus Operational Concept -- or 'HAVOC' -- in order to exploring concept aircraft that would be capable of taking astronauts to Earth's nearest planetary neighbor. The spacecraft involves sending what is effectively a blimp and a pair of astronauts on a month-long mission to float around Venus' atmosphere.
The engineers who worked on the Venus Operational Concept say that the astronauts would live and function in a floating habitat attached to the vehicle, which could be filled with helium to keep it afloat. It is estimated that Venus' atmosphere would help the vehicle keep itself aloft at an altitude of approximately 50 kilometers.
The developers of this concept envision future Venusian human settlements as anchored in the atmosphere and serving as planetary bases akin to the International Space Station.