Tucked away on the northwest side of Osaka Castle is the Hidden Bailey (Kakushi Kuruwa) — a kuruwa, or fortified enclosure, so narrow and easy to miss that many visitors walk right past it. Because it’s hard to notice from the main visitor route, it came to be called the “Hidden Bailey.” During the Edo period, it temporarily housed the Enshogura, a gunpowder magazine, and access was tightly restricted. Its angled stone walls and narrow passage still limit sightlines and movement today, and the enclosure now sits quietly among trees, rarely visited.

In the Yamazato-maru area on the castle’s north side, the Kokuinseki Hiroba (Inscribed Stone Square) was established in 1983 to mark the 400th anniversary of Osaka Castle’s construction. It displays more than 80 stones carved with kokuinseki — symbols believed to be related to the daimyo lords or stonemason groups who supplied them, though no specific family has been definitively identified. The stones are arranged into six zones by where they were found — Osaka Castle grounds, Ryuzoji-cho, Neyagawa, Kizugawa-guchi, Tamatsukuri-cho, and Other — rather than by which daimyo domain contributed them. Between 1620 and 1629, the Tokugawa shogunate (Japan’s ruling military government from 1603 to 1868) mobilized 64 western daimyo to rebuild the castle’s stone walls, and each carved mark is a small trace of that vast construction effort.

On May 8, 1615 (Keicho 20), during the final battle of the Summer Siege of Osaka — the campaign in which Tokugawa forces defeated the Toyotomi clan — Toyotomi Hideyori and his mother Lady Yodo are traditionally said to have met their end near here, in the former Yamazato-maru enclosure on the castle’s north side. The exact location is disputed among historical sources. In 1997, the City of Osaka erected a monument at this traditionally identified site. Lady Yodo was the daughter of the daimyo Azai Nagamasa and a niece of Oda Nobunaga, the 16th-century warlord who began the unification of Japan; she later became a consort of Toyotomi Hideyoshi, who built the original Osaka Castle. Nearby stands a memorial tower honoring attendants traditionally said to have died alongside them.

Gokurakubashi Bridge links the Honmaru with the Ninomaru (the castle’s second bailey) and offers one of Osaka Castle’s most photographed views — the Main Tower reflected in the inner moat. A lavish bridge of this name was built in 1596 by Toyotomi Hideyoshi to welcome envoys from Ming-dynasty China. After Hideyoshi’s death, its timbers were moved first to Hokoku Shrine in Kyoto, then later to Hogon-ji Temple on Chikubu Island. A Tokugawa-period wooden bridge stood in roughly the same spot but burned down during the Boshin War, the 1868–1869 conflict that ended the Tokugawa shogunate. The current bridge was rebuilt in 1965 using reinforced concrete while keeping traditional ornamental railings; it spans 54 meters across the inner moat.

Kita-shikirimon was one of several “shikiri” — stone ramparts and gates used to partition sections of the Tokugawa-era Ninomaru (the castle’s second bailey) — and stood on the north side of Nishinomaru, the western enclosure now occupied by Nishinomaru Garden. (Ninomaru and Nishinomaru are different, similarly named parts of the castle: Ninomaru is the broad second bailey ring, while Nishinomaru is the western enclosure within it.) The original gate was lost after the Meiji Restoration, and the current structure was reconstructed in 1965, differing in appearance from the Edo-period original. It is not normally open to the public, though it is occasionally opened for special events. The surrounding stone walls and moat still carry much of the area’s historic atmosphere.

Standing in the masugata courtyard at Kyobashi-guchi, the Higo Stone is the second-largest monolith at Osaka Castle, with a surface area of about 54.17 square meters — roughly the size of 33 tatami mats. It was long popularly said to have been transported by the daimyo Kato Kiyomasa, which is how it came to be called the “Higo Stone” (Higo being Kiyomasa’s home province). Current scholarship instead generally attributes it to the Okayama Ikeda clan, who were responsible for the Tokugawa-era reconstruction of this section of the castle — part of the tenka-bushin system, under which the shogunate assigned castle-construction labor to daimyo across Japan as a demonstration of loyalty and financial strength.

Aoyamon Gate stands at the northeastern entrance to the Ninomaru. Built around 1620 as part of the Tokugawa reconstruction, it was damaged during the upheaval of the Meiji Restoration and in WWII air raids; the gate standing today is a 1970 reconstruction. It combines a masugata courtyard — a rectangular defensive enclosure closed by two gates — with an unusual demasugata, an extended outer section that traps attackers even further. During the Edo period, the gate is said to have sometimes been called the “kimon,” or demon gate, because of its northeastern position, traditionally considered an inauspicious direction. Just outside the gate, the foundation of the former Soroban-bashi (a retractable bridge) is still visible.