Wat Phra Phutthabat, the temple of the holy Buddha footprint in Saraburi, is one of the most important Buddhist temples of Thailand, but since it is located a bit far from Bangkok and without any further attractions nearby foreigners don't come there as much as Thai. However for a Thai this is a place which every good Buddhist should visit at least once in their life. The kings of Ayutthaya went there every year, even though at those times the travel was still much more arduous than today, where it's just 2 hours of driving by car from the capital.
During the reign of king Songtham at the beginning of the 17th century, Thai monks were sent to Sri Lanka to make merit at a Buddha footprint there. Soon thereafter in 1622, a hunter named Bun discovered the footprint near Saraburi, though actually it was only a puddle in a depression of the rock. The king visited the place, declared it an authentic footprint and ordered the construction of the temple.
The Wat Thai Temple Blog wrote about this temple before. For those who speak German fellow Wikipedia Hdamm has a travel report on his website, also Ben wrote a report on his blog on some of the traditions during the pilgrimage to this temple.