Taiwanese can drive when they're 18 and vote when they're 20. But according to one of the city's most popular customs, they become adults when they turn 16. In Qing-era Tainan, a child reaching that age was a cause for celebration because 16-year-olds working on the docks and in workshops were entitled to adult wages, not the half-salaries younger employees received.
Since the 1740s, 16-year-olds and their parents have been going to the Kailong Temple on the seventh day of the seventh lunar month to celebrate this coming of age. The event is called Cixi because it coincides with lovers' day in Chinese tradition. Until quite recently those wishing to take part in the ceremony, which involves crawling under an altar three times, had to purchase special gowns, shoes and hats and prepare specific offerings to honour Qiniangma, the goddess believed to protect children under the age of 16.
Nowadays the clothing can be rented and offerings need not adhere to custom so closely. The city government has been promoting the event as a way to bring visitors to Tainan; even if watching teenagers wave joss sticks while their parents try to cram offerings on tables already buckling under the weight of fruit, rice and seaweed doesn't interest you, some of the associated folk performances and concerts might.
The image here was contributed by Rich Matheson, the photographer I attended the event with. Rich also pointed out this very detailed 2001 article on the event.