It's officially called Haesindang Park, in the small fishing village of Sinnam, about 5 hours by bus from Seoul.
The park offers over 50 wooden and petal penises donated by artists from all over Korea. Often they are of a whimsical sort, like a penis canon, or a laughing penis.
There's a heterosexual origin myth, about a woman named Auebawi, who drowned before she could marry (and have sex). To appease her spirit, the villagers hold a biannual festival and offer her homemade penis carvings.
Seems like that would make her even more upset, as she realizes what she is missing.
There's also a museum of "sexual iconography," an aquarium, and an arboretum.