Si Satchanalai was built as a satellite city of Sukhothai linked by the road known as Thanon Phra Ruang which is considered to be the first highway in Thailand. Si Satchanalai was founded in 1250 and built on the banks of the Yom River, protected by two hills. Si Satchanalai and the associated historical parks at Sukhothai and Kamphaeng Phet are listed by UNESCO as World Heritage Sites. So it's well worth a visit.
There are numerous temples, Buddha statues, and shrines in and around Si Satchanalai Historical Park. Before the founding of the Sukhothai empire, the area was a Western outpost of the Khmer empire. Si Satchanalai temples:-
Si Satchanalai Pedestrian suspension bridge
For those daring enough to try, it is possible to ride across the bridge.