In St. Petersburg, the grand city of the czars, they call them the “White Nights”: those 80 or so evenings, running from May to the end of July, when the city emerges from long months of cold and darkness and celebrates the brief return of nearly round-the-clock daylight. Residents of Russia’s cultural capital — situated a few latitudinal lines south of the Arctic Circle, at the eastern end of the Gulf of Finland — have been welcoming the summer with relief and celebration ever since Peter the Great founded the city in the early 18th century. (The czar named the new capital after his patron saint, St. Peter the apostle.)
http://travel.nytimes.com/2011/06/05/travel/russias-white-nights-in-st-petersburg.html?hpw