The cathedral has benefited from an £8m restoration over the last ten years, ready for today's anniversary of its completion in 1561.
Originally called the Trinity Church, the cathedral took six years to build and was constructed as eight churches around a central ninth church, each commemorating a military victory. It survived heavy shelling during the Russian Revolution in 1917, and even avoided being blown up by Napoleon in 1812, when rain dampened French fuses.
The cathedral is shaped to resemble a bonfire rising into the sky. It blends Russian, Byzantine and Islamic influences and is unique in Russian architecture.
An exhibition opens at the cathedral today to celebrate the life of St Basil, the 'holy fool' who was feared and respected by the tyrant Tsar Ivan the Terrible.
St Basil never wore clothes, despite the fact that it gets a bit parky in Russia, and criticised Ivan the Terrible, who ordered thousands killed in bloody purges. Yet Ivan personally bore Basil's coffin to his grave, where the cathedral now stands.
St Basil's has been the subject of a Google doodle once before -- last Christmas. The festive logo featured not one but 17 doodles, each linking to holiday-related symbols, places and food.
Other innovators and eccentrics who have been similarly honoured by Google include Britain's own steam-age badass, Richard Trevithick, and the Mr Men. Pioneers of dance, science, and spaceflight have also been honoured, but our favourite is the playable guitar logo.