The Tunnel of Love at Klevan, in northwestern Ukraine, is a working freight line, and the tunnel is the shape of a train. Nobody planted the trees along it and nobody prunes them. Three times a day a locomotive and its wagons inch up the branch to a wood-processing plant, shearing off whatever has grown over the rails, and the trees keep growing around the gap that leaves. The corridor now matches a wagon's width and height almost exactly, which is what you are walking through. For a few hundred metres near the middle the branches meet overhead with no sky showing at all, and the light on the rails goes green around you. The freight passes at walking pace and you stand off in the trees while it fills the space it cut. That is the moment the whole thing explains itself.
Two stories travel with the place. Guides will tell you Soviet planners put the trees in to screen military trains from aircraft, and the claim is everywhere in print and nowhere in the record. The other, that a couple walking the sleepers hand in hand will get their wish, sounds like village folklore but is younger than the photographs. The arch went around the world in pictures in 2011, a Japanese film crew followed, and only then did the wish settle onto the place. The tunnel is also seasonal. It knits shut as the canopy fills in May and is densest through June. By mid-October the green has gone over to amber and rust, fallen leaves bury the sleepers, and the rails run as two dark lines through colour. The arch thins week by week after that, letting more sky through, until November leaves a bare railway through bare woods. Nothing protects any of it. The line is private, the tunnel carries no conservation status at all, and its shape lasts exactly as long as the plant keeps ordering wagons up the track. If the trains stopped for a few seasons, the trees would close the gap.