At the start of the fourth leg, only four teams remain. At the third checkpoint, Shangri-La in China, they discover where they are headed next - Varanasi, one of the world's oldest living cities. For the first time on the journey, each pair will pass through three countries in one leg - starting in China, venturing through Nepal, before crossing the border into India. But in their way are the mighty Himalayas. Impossible to cross on foot, the teams have to fly to Kathmandu, the capital of Nepal, to restart the race. From Kathmandu, teams can veer west taking in more of Nepal or head directly south to the border with India. Leaving China behind, the remaining pairs are catapulted into two new countries, having to navigate new languages, currencies, cultures and customs, not to mention completely different transport systems as they swap bullet trains for rickety buses on Nepal's notoriously treacherous roads. Once teams cross into India, the race is on to reach the fourth checkpoint. The leg culminates in a thrilling race through the winding, ancient streets of India's holiest city, Varanasi, situated on the banks of the River Ganges.