Children ride horses during a horse race as part of the Naadam Festival celebration at Khui Doloon Hudag outside Ulan bator, July 10, 2015. Naadam is the biggest event in the Mongolian calendar held from July 11 to 13, on the anniversary of the Mongolian revolution of 1921. Concerts, fairs and traditional sports like wrestling, archery and horse racing are held during the celebration. REUTERS/B. Rentsendorj