This boulevard inside Jingū-gaien (the public outer gardens of Meiji-jingū) is lined with gingko trees. For a couple of weeks around late November and early December, the trees – which for some reason in Tokyo are always sculpted into soft-serve like spires – turn golden yellow (which means when the leaves fall the streets are literally paved with gold.
The gingko is actually Tokyo's official tree; once you realise this you'll see the motif of the fan-shaped leaf everywhere. For Japanese, Ichō-namiki is an instantly recognisable image of Tokyo, often used as visual shorthand for the city in TV and film.