It is built on two raised platforms of landfill supported by sheer walls of cut rock, using a technique called burdock piling, each overlooking a moat.

There are two places to cross the inner moat, Gokuraku-bashi Bridge (located in the North) and Sakuramon Gate (main sentry point in the South).

Located within the Hommaru is the Main Tower, the Kimmeisui Well, the Japanese Garden, the Takoishi (Octopus Stone), the Gimmeisui Well, the Miraiza Osakajo Complex, the Kinzo Treasure House, and the "Timecapsule Expo'70".

As with almost all Japanese castles from the Azuchi-Momoyama period onward, the tenshu (天守, main keep), the most prominent structure, was used as a storehouse in times of peace and as a fortified tower in times of war, and the daimyo (大名, feudal lord)'s government offices and residences were located in a group of single-story buildings near the tenshu and the surrounding yagura (櫓, turrets).

[5] Although the Toyotomi forces were outnumbered approximately two to one, they managed to fight off Tokugawa's 200,000-man army and protect the castle's outer walls.

Ieyasu, in outrage, sent his armies to Osaka Castle again, and routed the Toyotomi men inside the outer walls on June 4.

[4]: 153 As the Toyotomi clan no longer existed,[6] the Tokugawa shogunate expressed their desire to move their center of government into Osaka.

[7] For a while, the shogunate's plan to move to Osaka was abandoned, but was reinstated by Tokugawa Hidetada, who had a strong desire to establish a unified imperial and military government.

[9] Then, the project of reconstructing Osaka castle as a new base of the shogunate was entrusted to Tōdō Takatora and Kobori Enshu.

Many of the stones were brought from rock quarries near the Seto Inland Sea and bear inscribed crests of the various families who contributed them.

Construction of the tenshu started in 1628 and was completed two years later, about the same time as the rest of the reconstruction, and followed the general layout of the original Toyotomi structure.

[14][15][16] In 1843, after decades of neglect, the castle got much-needed repairs when the bakufu collected money from the people of the region to rebuild several of the turrets.

The castle is open to the public and is easily accessible from Osakajōkōen Station on the JR West Osaka Loop Line.

It is a popular spot during festival seasons, and especially during the cherry blossom bloom (hanami), when the sprawling castle grounds are covered with food vendors and taiko drummers.