Osaka Castle is a castle located in the central city district of Chūō-ku.

It is one of the most famous and important buildings in the country, and played a fundamental role in the unification of Japan in the 16th century, during the Azuchi-Momoyama period.

The castle is located within Osaka Castle Park (Osaka jo Koen), one of the largest green spaces in the city.

It was built on the northern end of the small Uemachi-daichi plateau (12 km long and 2.5 km wide), and its base is therefore raised from the rest of the park and the entire city.

The castle rests on two raised earth platforms supported by two high perpendicular walls of cut rock of the plateau, each overhanging a moat.

The central building of the castle is five floors high outside and eight floors inside, which together with the natural height difference of the plateau guarantee a high level of protection to its inhabitants in case of siege.

Just like the Imperial Palace in Tokyo, it sits upon the rests of previous megalithic structures that serve as anti-seismical foundations.

The base of the structures was in fact built much earlier than the castle itself, and it’s made of polygonal megalithic walls.

The craftsmanship of the lower polygonal walls, when compared to the upper actual structure of the castle, shows a clearly different constructive style.

The Octopus Stone

The megalith known as the Octopus Stone, called Taiko-ishi by the Japanese, is a large megalithic stone near the Sakura Gate, one of the entrances to the palace.

Measuring 5.5×11.7 meters (18×38.4 ft) and over 130 tons, it is one of the biggest megaliths in the whole area and most likely stands as the remnants of a much bigger structure.

Who moved such a massive megalith, when, and why, are still unanswered questions.