Along the way it flows through Vientiane, the capital of Laos, and Phnom Penh, the capital of Cambodia. Near to Phnom Penh, the Sab River connects the Mekong to Tonle Sap, sometimes called the Great Lake, with Siem Reap, home to Angkor Wat, on its north side. The lower Mekong, which flows through Cambodia and Vietnam, offers visitors a wonderful highway to help them explore this fascinating region, which boasts such diverse peoples, landscapes, and cultures.
The people here depend on the river for both income and sustenance: they fish in its waters and farm on its shores. The Mekong basin is home to the biggest inland fishery in the world, and as you explore by boat, you will come across numerous fish farms. Throughout Vietnam the busy river, complete with floating markets and constant frenetic activity, is entrancing.
Crossing the border to Cambodia, you immediately notice the difference - here life is led at a more leisurely pace, with farms, settlements and small-holdings looked after by relaxed family groups. This fascinating insight into a rural lifestyle contrasts with the busy town centres, with rich heritage and traditions enriched by 2,000 years of human history. Visit temples and palaces, pagodas and monasteries. Here you can see fascinating architecture, and learn about a whole variety of religions and civilisations.
The delta region is particularly biologically diverse, home to iconic species such as the Siamese crocodile, the sarus crane, Mekong giant catfish, Mekong stingray and giant ibis. Lucky visitors might catch sight of the magnificent and extremely rare Irrawaddy (Mekong) river dolphin, while the verdant rice fields are worked by hardy humped Brahman oxen.
The cities of Siem Reap, Phnom Penh and Ho Chi Minh bear witness to the region's chequered past. The Khmer empire flourished from the 9th to 15th century and ruled over most of mainland South East Asia. Exploring the temple complexes of Angkor Wat and many more from Siem Reap is an extraordinary experience, especially as you learn that this region was the largest pre-industrial urban centre in the world, home to great art, architecture, culture, religions and universities.
From Phnom Penh you can learn more about Pol Pot's regime, with a sobering visit to Cambodia's infamous Killing Fields and the Khmer Rouge's grim Tuol Sleng S21 detention centre (Genocide Museum). In contrast, the Royal Palace and bustling Central Market, Silver Pagoda and National Museum introduce another face of the city.
Ho Chi Minh City is a strident and energetic blend of old and new, East and West. French influences mean the coffee is strong and the patisserie excellent. You will take your life into your hands as you cross the teeming roads, exploring the Reunification and War Remnants museums.
Temperatures are highest in March and April, whilst the 'dry' season is relatively short (November to February), but you can in fact travel on the Mekong for most of the year - some river cruise operators do not sail from April to July, and arguably for good reason. Whenever you go, temperatures will be warm, mainly in the high twenties.