Odawara Castle is a mountain castle located on a hill above Odawara City in present-day Kanagawa Prefecture and is a designated national historic site. It was built in 1417 by Oomori Yoriharu and greatly expanded by Houjou Souun when he took it in 1495. His son Houjou Ujitsuna made it his main stronghold, and so it remained for three more generations of the clan. Its extensive defenses repelled attacks by great warlords such as Uesugi Kenshin and Takeda Shingen. Toyotomi Hideyoshi took the castle in 1590 after the Houjou surrendered to him in the Siege of Odawara. He awarded it to Tokugawa Ieyasu after destroying most of its fortifications along with the Houjou lands.

Tokugawa gave the castle one of his senior retainers, Ookubo Tadayo, after the completion of Edo Castle, and it remained in the hands of the Ookubo Clan aside from a few decades in the late 1600s until the Meiji Era, when the castle was destroyed in 1870–1872 in obedience with imperial decree.

The area became Odawara Castle Park (also known as Castle Ruins Park) in 1950. The park includes an art museum, local history museum, city library, amusement park, and zoo. The present (historically inaccurate) structure, which mimics the much-reduced form of the castle in Ookubo Tadayo's time, was rebuilt in 1960 out of reinforced concrete to celebrate the 20th anniversary of the proclamation of Odawara as a city. Tokiwagi Gate (常磐木門) in the inner citadel, Akagane Gate (銅門) in the outer citadel, and Umade Gate (馬出門) were reconstructed in 1971, 1997, and 2009, respectively, in more historically accurate representations of their late Edo forms.