The walls of Osaka Castle, or the walls on which it stands, are built with massive granite blocks, some of which reach remarkable size and weight. A significant example is the Octopus Stone (Tako-ishi), located near the Sakura Gate, measuring approximately 5.5 meters (18 feet) by 11.7 meters (38 feet) and weighing over 130 tons (286,600 pounds).
The construction technique used for the walls is known as ishigaki, which involves cutting and assembling stones without the use of mortar, ensuring structural stability. This is a construction technique similar to those found worldwide, defined as polygonal, where the stones are interlocked in a sort of 3D puzzle, fitting together so precisely that they exhibit earthquake-resistant properties without requiring mortar to hold them in place.
The castle was built in the second half of the 1500s and was later reconstructed in the first half of the 1600s.
In the Places section of the site, you can filter on the map to find locations worldwide featuring stones crafted in this manner.
To appreciate some of the megaliths that make up the base of the structure, it is recommended to view this post on Reddit.