Tucked away on the northwest side of Osaka Castle lies the Hidden Bailey (Kakushi Kuruwa) — a narrow bailey that many visitors miss entirely. Because it is difficult to notice from the main route, it is generally thought to have been a place where soldiers could be concealed. Its angled stone walls and walkways still restrict sightlines and movement, and today it remains a peaceful forested corner of the castle grounds.

Located in the Yamazato-maru on the northern side, the Inscribed Stone Square was established in 1983 to commemorate the 400th anniversary of Osaka Castle’s construction. It displays around 80 stones bearing engraved marks — clan crests, stonemason symbols, and characters — from the 64 feudal domains mobilised by the Tokugawa Shogunate to build the castle’s stone walls between 1620 and 1629. Each inscription is a historical record of the political and logistical forces behind one of Japan’s greatest castle construction projects.

On May 8, 1615, during the Summer Siege of Osaka, Toyotomi Hideyori and his mother Lady Yodo are said to have taken their own lives here in the Yamazato-maru compound, marking the end of the Toyotomi clan. The City of Osaka erected a monument at this site in 1997. Lady Yodo was the daughter of warlord Azai Nagamasa, niece of Oda Nobunaga, and concubine of Toyotomi Hideyoshi. Nearby stands a memorial tower for attendants traditionally said to have died with them.

Gokurakubashi (“Bridge to Paradise”) connects the inner Honmaru with the Ninomaru and offers one of the most iconic views at Osaka Castle — the Main Tower reflected in the inner moat. A luxurious bridge of this name was built by Toyotomi Hideyoshi in 1596 to welcome envoys from Ming China. After Hideyoshi’s death, its timbers were moved first to Hōkoku Shrine in Kyoto and later to Hōgon-ji on Chikubu Island. A Tokugawa-period wooden bridge stood in roughly the same place, but it burned in the Boshin War. The current structure was rebuilt in 1965 using reinforced concrete while retaining traditional ornamental railings. It spans 54 metres across the inner moat.

The North Partition Gate was one of the gates used to divide sections of Tokugawa-period Osaka Castle. The original gate was lost after the Meiji Restoration. The current structure was reconstructed in 1965 and differs from the Edo-period gate that once stood here. It is usually closed to the public but is sometimes opened for special events. The surrounding stone walls and moats still preserve much of the historic atmosphere of this side of the castle.

Towering in the masugata of the Kyobashi Gate, the Higo Stone is the second-largest giant stone in Osaka Castle grounds, with a surface area of approximately 54.17㎡ — roughly the size of 33 tatami mats. It was long said to have been brought by Kato Kiyomasa, which is why the stone came to be called “Higo Stone,” but current interpretation generally connects it with the Okayama Ikeda clan, which handled this section of the Tokugawa reconstruction. Iron wedges embedded beneath the stone helped stabilise it.

Aoyamon Gate stands at the northeastern entrance to the Ninomaru. Constructed around 1620 as part of the Tokugawa reconstruction, it features a masugata courtyard and a distinctive demasugata — an extended outer section that further traps invaders. During the Edo period, the gate was considered a “kimon” (demon gate) due to its northeastern position, and was typically kept closed to ward off misfortune. Damaged in the Meiji Restoration and WWII air raids, it was reconstructed in 1970. The nearby Soroban-bashi (retractable bridge) foundation is still visible outside the gate.