Red Square

 was in Moscow, Russia. The Seventh Doctor, Ace, Markus Creevy and Raina Kerenskaya attended the ceremony in Red Square marking the fiftieth anniversary of the October Revolution on 7 November 1967. They saw Yuri Gagarin and Valentina Tereshkova, the first person and the first woman in space respectively, on the podium. The Doctor explained to Ace that the celebration of the October Revolution was held in November as Russia was still using the Julian calendar, which was eleven days behind the Gregorian calendar, in 1917. (AUDIO: Thin Ice)