"Imperial Palace running" around the outer loop of the Imperial Palace (Chiyoda Ward, Tokyo) is popular. At lunch, runners stream past Palaceside Building in Takebashi (photo). Weekdays see thousands; Sundays over ten thousand. Wednesday evenings, when overtime is less common, draw especially large crowds. I was surprised to see people running on snowy mornings, though...
Facilities like RunPit by au Smart Sports in Palaceside Building, with lockers and showers, see evening queues daily; events such as the "Takebashi Ekiden" (Mainichi Running Club, November) thrive. As health awareness rises, the convenient ~5 km loop with no traffic signals mid-course is a main draw. After the earthquake, some started running to build stamina for walking home. With more bicycle commuting post-disaster, conflicts between pedestrians, cyclists, and runners at certain times are a concern. Chiyoda Ward has set up an "Imperial Palace Area Committee" to study manners and environment and draft "new rules" all can accept. Runners may get carried away—but please run counterclockwise (keep left), single file in narrow spots, and avoid reckless passing—with consideration for others.