Sycamore Gap Tree

How do you replace something that is irreplaceable? That is the struggle facing a community in northern England where vandals cut down a landmark 300-year old tree along Hadrian's Wall. The Sycamore Gap Tree was a solitary tree in an historic space, so it leaves a visible hole. Should they build a memorial to mark the spot? Plant a replacement tree? Install an artificial (presumably artistic) facsimile?