The Pit of Voles, also known as the Pit, the Sewer, the Reeking Pit of Open Sue-age, and fanfiction.net, is the biggest source of badfic. This is because, while there are site rules about spelling, grammar, and content, the site is so huge that they are rarely enforced. It also hosts fanfiction for a wide variety of fandoms, making it very easy for users to write stories set in worlds they know almost nothing about.
Some consider "the Pit" to be an unnecessarily derogatory term for fanfiction.net. Authors of goodfic also post in the Pit, despite its reputation, because it is the most popular fanfiction site on the Internet and stories there are very likely to be reviewed.