A one-off special to herald the start of the Commonwealth Games. Some of the nation's best-loved presenters - Clare Balding, Denise Lewis, Anita Rani, Dan Snow and Reggie Yates - travel around the globe to marvel at seven diverse natural wonders and meet some of the two billion members of the Commonwealth. They venture to the oldest desert on the planet, the most pristine rainforest, the world's greatest waterfall, the largest mangrove swamp, the richest coral reef and the world's most spectacular fjordland. The final wonder is found deep in a cave far closer to home. Along the way they discover what it means to part of the Commonwealth today.