Hand-painted metal tunnel #2525. Viewing ports became popular early in the 20th century after they appeared on real railroad tunnels that went through the Alps. Measurements shown with tape measure in photos. Note photo a catalog picture from 1909. (This one has a tree on top; there was some variety in details.

Some fading and a few paint chips on this one, but the castle tower, chalet, a nice path with a railing, and railings in the viewing ports.