It is a nationally designated important cultural property in the Imperial Palace, the former Edo Castle Outer Sakurada Gate. The outer Sakurada Gate is famous for the "Sakurada Gate Outside Incident" of the assassination of Naoya Ii by the ronin of the Mito clan in 1860. This incident was caused by the suppression carried out by the shogunate, the "Great Prison of Ansei". After the incident, the authority of the shogunate was lost, and the Edo period, which lasted 265 years, came to an end.