Week Three: Bonus Question

In the spring of 2004, a well-known actor and a friend took off on their own Amazing Race of sorts, but on their motorcycles, and with a camera crew (the trip was later turned into a six-part TV series). They had this to say about Mongolia:

There were no roads, just tracks that wandered off in different directions. When you asked someone for directions, they'd say, "Go down that valley, and at the second valley on your left, turn left. Then you'll come across two clumps of trees atop a hill. When you see them, you're headed the right way."

(Actually, that sounds like Ireland to me)

Who was the well-known actor, and what was the name of the TV series?