Kawaguchi was Japan's foundry town. For centuries its workshops cast iron pots, kettles and temple bells from the sand and clay of the Arakawa, and by the twentieth century the town was famous for its cupola furnaces, whose chimneys filled the skyline. A classic 1962 film, set among the foundries, made the town a symbol of working-class Japan. Most of the furnaces have gone, replaced by apartment towers for Tokyo commuters, but a few workshops still cast metal in the old way.
This finish lies on the southern edge of the city, near the Arakawa, where Kawaguchi faces Tokyo across the river. Akabane, on the Tokyo side, is famous for its cheap, cheerful bars, where you can drink and eat for a few coins standing at a counter, and on weekend evenings the narrow lanes near the station are packed.
The Arakawa riverbanks are broad and green, with sports fields, cycle paths and reed beds, and the levee offers views over the city and, on clear days, to Mount Fuji. The river is a reminder of the floods that once threatened the low-lying plain, and the massive embankments were built to keep the water out.
Coming back from the Boso peninsula, the final stretch crosses Tokyo on the expressways or loops around it, and the traffic can be heavy. Plan for delays on Sunday evenings, and take care on the busy surface streets near the river.
Fuel and konbini are easy to find on the main roads. After a long day on the Boso coast, a seat at a counter in Akabane, with a cold beer and a plate of grilled skewers, is a deeply Tokyo way to end the ride.