I chose the trek up Langtang valley, because ascending from just 600m to 5000m, the trail passes through an ever changing climate and offers an exceptional diversity of scenery and culture. In addition, although quite close to Kathmandu, it was lightly populated and saw few tourists. It would also take just a week. I wasn't disappointed.
Although lightly populated, there were a few basic places to stay offering surprisingly good food.
Looking up the Langtang valley
Although the path is clearly marked, I thought it best to hire a guide/porter (he insisted on carrying my rucksack, honest)
Views of Kyanjin Gompa from Tsergo Ri (highest point of the trek at 5000m). And it felt pretty high. For the first time on the trek, climbing this small peak was exhausting. At every step I was gasping for air. That night I had halucinations caused by mild altitude sickness but a week before two people weren't so lucky - they died. The key was to sleep the night at a place lower than the highest point reached that day.