If you ever visit La Paz in Bolivia you must attempt the Death Road descent on a well worn mountain bike. A better history than I can write can be found here, but in short since 2006 a safer bypass was opened to accommodate traffic away from the notoriously dangerous stretch of read, so now the hordes of bikes screaming downhill made up 98% of the traffic on the day I took the plunge.
I never felt in any danger on my bike, but the very narrow (no more than 3.2m wide), poorly graded dirt road cut into the mountain resulting in sheer cliffs (with no guard rails) on one side would make passing other vehicles and regular traffic a nightmare. I can easily see how the road got its name.
We started at La Cumbre (4700m), an hour or so outside La Paz and finished three hours later at Yolosa (1200m). We descended approximately 3500m over 63 km, I barely touched the peddles but as you can imagine I was constantly on the breaks.
It was a really cool experience, only slightly marred when I somehow bent the rear derailleur 90 degrees, bringing an end to that bike! With only 15 minutes to go I borrowed the guides bike and completed the journey without any further problems.
We were then taken to Coroico for a buffet lunch at a hotel with a fantastic view, where I cooled off after the hot dusty ride by having a short swim in the hotel pool. A really enjoyable day, all the better for being in a small group (consisting of me and three hungover Chileans) and being one of the first groups down the mountain.
Photos were taken by the tour guide, and can be found here