At 2700 miles (4350km), the Mekong is the longest river in south-east Asia and the twelfth longest in the world. It flows through six countries, rising in China in Qinghai province at an altitude of 16,000ft (4900m), flows through eastern Tibet and Yunnan province. Thereafter it becomes an international border first between Burma (Myanmar) and Laos, then Laos and Thailand. It goes on through Laos, Cambodia and Vietnam before it reaches the South China Sea. The first half of its length when it is known as the Upper Mekong, it passes through a wild, rugged, empty landscape and its turbulent waters are not easily navigable.

The Lower Mekong (from the Burma/Laos border onwards) is a more gentle at a lower altitude and this is where most cruises tend to take place. Commercial vessels are common here, too, usually carrying agricultural products and timber. There are still highlands here, often covered in dense forest, as well as open plains, paddy fields and grazing animals, and the river passes through lakes, dividing into two branches below Phnom Penh: one part continues as the Mekong, the other as the Bassac. The delta is a vast 25,000square miles (65,000sq km) and is in part swampy. It is home to a huge biodiversity – only the Amazon has a higher level. Huge fish include the Mekong Freshwater Stingray and the Mekong giant catfish. There are otters and fishing cats, crocodiles and, occasionally dolphin. The Mekong flows through the Golden Triangle and its banks have been home to many different cultures and civilisations. There are golden Buddhas and orchid gardens, working elephants and glorious temples, floating houses and a museum devoted to what was once the region’s most lucrative cash crop – opium.