Vietnam

Hai Van Pass (Mountain pass between Hue and Danang): Whole route is only possible on a motorbike, but if you plan on going toward Hue anyways, you can also take the train. The train doesn’t go the whole way, but you get to experience parts of the pass (the busses/cars go through the tunnels and you will skip the pass all together)

Highlight of Vietnam: Ha Giang loop ( 3 days quite exhausting on a motorbike, but 4 days on a motorbike would be too much for me personally). Make sure to check the size of the group, some groups are 15-20 people including parties all night long and dorm rooms.