On 15 April 2005 Vittori participated in a second taxi-flight to the International Space Station (ISS), Soyuz TMA-6, returning to Earth on 24 April in the Soyuz TMA-5 capsule. He became the first European astronaut to visit the ISS twice and conducted experiments in upper limb fatigue in astronauts and germination of herbaceous plant seeds for possible space nutrition.
The astronaut also had a painting of the artist George Pusenkoff titled Single Mona Lisa (1:1) with him and took photos with it on the International Space Station. It is the ultimate continuation of the project "Mona Lisa Travels" developed by Pusenkoff and could only be realized under difficult conditions. The authorities found the idea good in theory, but constantly put forward new reasons why the project was unrealizable. Only when George Pusenkoff wrote to the then Italian ambassador in Russia, Gianfranco Facco Bonetti, the possibility of realizing the idea arose. The connection between science and art, which was also important in Leonardo da Vinci's life, found here an "actualization" in the form of this journey of an image of Mona Lisa into space. For the action, Pusenkoff's painting was removed from the frame so that it could be rolled. On April 25, 2005, Vittori took the painting back to the Earth with him.