While there have been shrines in some form on this site since the fifth century, the current structure which forms Wat Phu was constructed by Suryavarman II (who was also responsible for the construction of Angkor Wat).
The construction has been integrated into the natural landscape in a manner unlike any other Khmer structure, with a natural spring feeding water directly into the complex.
The site draws on an axis from the summit of Phu Kao (the mountain it backs onto) down to the bank of the Mekong and comprises a collection of temples, shrines and waterworks. As with the majority of Khmer temples, Wat Phu is orientated to the east and including its barays the entire complex stretches for over one kilometre from the spring at the base of Phu Kao.
Upon entering the site from the ticket office, you'll pass down what was once a causeway flanked by two barays. After this there are two pavilions, most often referred to as the Men's and the Women's Pavilions -- it's thought that these were worshipping halls -- one for women, one for men -- though the final verdict isn't in. While the roofs are gone, the buildings themselves remain in fine condition and restoration work is being conducted in conjunction with archaeologists from around the world. Behind the Women's Pavilion sits the Nandi Pavilion -- it was from here that the Royal Road once commenced for the long trek to Angkor Wat. Nandi was the mount of the Hindu god Shiva.
After the Nandi Pavilion, the climb gets steeper and the frangipani more dense. Following the climb you'll reach the main complex which was originally devoted to the Hindu god Shiva, but was subsequently transformed into a Buddhist shrine in the 13th-14th century. While the sanctuary roof is long gone, the walls and foundations remain solid. When in working order, water from the spring would run down from the cliff-face via a series of aqueducts into the rear chamber where it bestowed a permanent shower upon the linga. After bathing this centrepiece the water was then piped further along and out to a public point where worshippers could bathe in it.
Beyond this central sanctuary are a number of oddities, including a crocodile rock and an elephant rock -- both are very popular attractions, particularly with locals.
A particularly good time to visit is in April and May, when the frangipanis are in full bloom, making the site very photogenic.
How to get there
Wat Phu is located 10 kilometres southwest of Champasak along a sealed road and takes 15 to 20 minutes to reach by tuk tuk. Most people would be happy spending two hours on site, which gives enough time to make the tiring climb to the top of the hill where most of the interesting features are. If cycling, the road from Champasak is fairly straight, bumpy and devoid of any shade so don't forget your hat, though there are plenty of shops along the way selling drinks. Morning is the best time to visit light-wise, particularly for photographs, while in the evening the sun disappears behind the mountain by about 17:00.