Sky Walk Wat Phra That Doi Wao

Two things happening at once here: a functioning Buddhist temple on a hill in Mae Sai, and a glass skywalk that pushes out over the slope so you can look straight down through your feet. That combination is what makes it worth the climb. You wander the temple grounds, then step onto open air and get the whole Chiang Rai countryside and the border region beyond it laid out in front of you.

Go early. The gates open at 7am and the light in the first couple of hours is softer, the walkway quieter, and you'll actually get a photo without someone else's elbow in it. Late afternoon works too if you don't mind company. The hilltop catches wind, so a layer in your bag is sensible, and shoes with some grip make the glass sections less of a nervous shuffle. Remember it's an active religious site as well as a viewpoint, so dress and behave accordingly.