The Ara River rises in the Chichibu Mountains of Saitama Prefecture, from where it flows southeast for some 140 km to reach the capital and discharge itself into Tokyo Bay. As its name (which means "rough") implies, it used to be a violent river, swelling after heavy rains and raging across the wide flood plain of the Sumida, as the river is known in its lower reaches.

The big river was also an important natural defense for the shogun's capital, and consequently throughout the Edo Period (1603-1867) few bridges were allowed to span it. Instead, ferryboats were used to make the crossing, operated under regulations enforced by the shogunate.

The 1830s woodcut illustrations by Hasegawa Settan show one of these ferries at Toda on the northwestern edge of the city. The boat, with a horse and several passengers aboard, is about to reach the shore, where more horses and passengers wait to be shuttled back. Meanwhile, another ferry is preparing to leave the other shore and, although the river looks quite high, all the horses we see appear quite at ease on what must have been a late afternoon, judging from the black silhouette of Mount Fuji and the surrounding ranges against the bright western sky.