Peru -- Primarily Machu Picchu (Dec 2010)

Note the stone retaining walls. Apparently all of this dates from Inca times. However, I suspect the Peru national park service has to do some maintenance on this. It's VERY steep and I'd think between the weather and ~400 hikers a day, stones would occasionally work loose.

The trail takes a left trun (thru the retaining wall) at about where the two people ahead of me are in this photo.

As I said in connection with an earlier photo, the time in Cuzco made for a pretty effective altitude adjustment. I stopped to get my breathing down to roughly normal perhaps every 100 feet of vertical climb on this trek (and I didn't really need my jacket for most of the way up), but it wasn't too bad.