Professional Indian mountaineer Arjun Vajpai today scaled the world's sixth highest mountain Cho Oyu.<br/><br/>The 23-year-old reached the summit before dawn along with his sherpas and another expedition member after leaving from Camp 3 post midnight.<br/><br/>With the Cho Oyu summit, Arjun has climbed five of the 14 highest mountains in the world that tower over 8000 metres and holds world records as the youngest summiteer on Mount Lhotse,<br/>Mount Manaslu and Mount Makalu.<br/><br/>Arjun unfurled the Indian tri-colour on the little bump that marks the Cho Oyu summit after a 7 hour, all-night climb through rocky steps, mixed snow and a long traverse to the top. <br/><br/>The Mount Cho Oyu 2016 expedition was a personal challenge for the young mountaineer because he had suffered a paralytic attack during his first attempt in 2011 and Arjun had to work his way back to physical fitness to climb again.