The stones, believed to be among many quarried into usually square shapes, were found at a depth of two to five meters in areas about five to 30 meters off the coast. One of the stones is approximately 90 centimeters by 90 centimeters by 2 meters, about the same size as stones used in the central part of the castle grounds.
The stones are believed to have been quarried in 1606 in a project carried out by feudal lords under the order of the Tokugawa shogunate (1603-1867).
Some of the stones had holes called ya-ana that are thought to have been drilled into them to make them easier to quarry.
According to documents, about 3,000 ships carried stones quarried on Izu Peninsula to Edo for the reconstruction project.
Story: Daily Yomiuri Online | Photo: Wikimedia Commons