Little known but important: the old London Magazine near the Serpentine, Hyde Park. An 1805 Palladian-style villa, it once housed naval cordite for the defense of London. In 1911, war threatened over the Agadir Crisis. Observing the Magazine was unguarded, Churchill sent a marine detachment. His decisive action helped convince Prime Minister Asquith to appoint him First Lord of the Admiralty, where he prepared the Royal Navy for war. For years abandoned, it reopened in 2013 as an art gallery then a restaurant. (Zaha Hadid Architects)