Vindolanda is well worth a visit. A little more gung-ho in its approach to the archeology but that's not necessarily a bad thing in context.

There is an awful lot of footfall along the wall in general, and that segment past Sycamore Gap must be the busiest. Wikipedia tells me there used to be other mature sycamores there but that they were removed "for unknown reasons" but I can see why nothing can get established now.