Karmila Purba revs her motorbike under the lights of an Indonesian night carnival and rides up horizontally inside a wooden cylinder called Satan's Barrel, drawing gasps from spectators looking down into the drum. The gravity-defying daredevil is among a handful of women that perform the stunt in Indonesia, zipping around a structure more commonly known as the "Wall of Death." Female "Wall of Death" riders are "extremely rare," the 23-year-old told a journalist before the show.