315 km from Cueta (spain, but on the African side) to Fez (Morroco). A four-hour harrowing ride through mountains at night where every 75km there was another accident. The ride back during the daytime was one of the most beautiful sceneries I have every seen. Cost was $100 US for the whole taxi.

I have also done another taxi ride from Dong Dang (boarder of China and Vietnam) to Han'oi. Cost was $35? and was about 200km for the whole taxi.

I have taken a minibus from Siem Reap to the Thai border. That was only 160km, but took us 5 hours the road was so freaking bad.