The Sycamore of Hollerich

Somebody has photographed this sycamore and nobody has measured it. The photograph is on Wikimedia Commons, matched to the register's coordinate to within a third of a metre, and beyond that there is one line in a regulation. No age, no girth, no height. The regulation does give its reasons for keeping the tree, and it names two rather than one: how it sits in the landscape, and its biological interest. What that biological interest consists of is not spelled out in any source we found, which is a shame, because on a mature tree it is usually the more interesting half of the answer. It stands on the Hollerich stretch of the Petrusse valley path, the far end of the same walk that passes the braced beech under Bastion Beck. The valley runs on westward out of the fortress rock and through Hollerich, and the path stays public the whole way. From the bus stops on Rue de Bouillon it is about ten minutes down. Neither this sycamore nor the one down in Pfaffenthal has ever been dated. If you know anything about either of them, including who put them in and roughly when, we would take it.