Beijing is a vibrant jumble of neighborhoods and districts. It's a city that was transformed almost overnight in preparation for the 2008 Olympics, often leveling lively old hutongs (alleyway neighborhoods) to make way for the glittering towers that are fast dwarfing their surroundings. Still, day-to-day life seems to pulse the lifeblood of a Beijing that once was. Hidden behind Beijing's pressing search for modernity is an intriguing historic core. Many of the city's ancient sites were built under the Mongols during the Yuan Dynasty (1271-1368). A number of the capital's imperial palaces, halls of power, mansions, and temples were rebuilt and refurbished during the Ming and Qing dynasties. Despite the ravages of time and the Cultural Revolution, most sites are in good shape, from the Niujie Mosque, with Koranic verse curled around its arches, to Tiananmen Square, the bold brainchild of Mao Zedong.