If you thought you had seen all the temples in Thailand 'if you've seen one, you've pretty much seen them all', then there is still this temple. 'The Temple of Hell', or a collection of gruesome sculptures that depict what will happen to you if you end up in Hell. 40km south of Chiang Mai, so it will take you an hour to get there. And definitely not for the faint of heart.
Bring a stack of 10 THB coins if you want to see the sculptures move and/or hear them scream.