Riding the Manali to Leh highway on rented Enfields, then on to the Khardung La pass.
Only around 300 miles in all, but these aren't 'normal' roads. A handful of passes in the Himalayas claim the title of 'world's highest motorable road', and Khardung La is one of them. The sign at the top states 18,380 feet, whereas other sources claim 17,582. Either way, it's fairly high.