If you’re up for it, there is a wonderful trail to the top of Fansipan mountain. Depending on the time of the year, the trail can be quite technical. You would also need to have a local guide with you. I think there may be a way for you to hike without one, but I would recommend hiring one. They’re strong and fast and can even carry your packs if you get tired. They do speak English, so you’ll be able to chat with them along the trail and learn more about the minority communities who live in the mountains of Sa Pa. My recommendation is to go up in one day and take the gondola down (oh yes, I should mention you can take the gondola up as well if you don’t want to hike at all) instead of breaking it in two days (which was what I did before).