The underside of the leaves of Rhododendron traillianum are apparently sweet-smelling, but I didn’t think to try it so I can’t describe the scent. Perhaps Douglas will describe the scent in a comment.
This species is native to southwest China and Tibet. The Flora of China provides a detailed description, while the American Rhododendron Society provides a quick factsheet. More images of Rhododendron traillianum can be found in the photo galleries of Asperupgaard, a Danish garden.