Vanessa O’Brien has become the first American woman to reach the top of the world’s second highest mountain known as K2. The mountain reaches 8,611 meters above sea level. O’Brien is a 52-year-old former banker from New York. She led a 12-member team of international climbers. She placed the United States flag on K2’s top - or summit - on July 28. K2 is on Pakistan’s border with China. It is one of the world’s most dangerous mountains to climb. “A proud day for #woman everywhere at the top of #K2, the world's second highest mountain,” O’Brien announced on Twitter shortly after reaching the top on Friday.