What is a Pon?
Pon or Jum'at Pon, is an Indonesian local holiday which requires to go up the Kemukus mountain aka Sex Mountain, find a random person doing the same and have sex with him or her, no matter if you're already engaged in marriage with someone or not.
Then you need to do so seven times to complete the quest for making seven wishes true, i.e. visit the mountain roughly every 35 days during the year. You may do it with a person from the first time, if you had exchanged contacts.
The origins of the holiday take place in a legend about prince and his stepmother, whose affair was uncovered by local people. They were chased by islamic soldiers from neighbouring provinces to this mountain and supposedly killed here.
The tradition requires to do something more obscene than said prince and stepmom, so your wishes will be granted by her spirit.
Holiday practice was active from XVI century to 2014 until authorities banned it due to high numbers of STD it caused.