Check online for the opening schedule and somewhat complex admission details for this imperial palace and garden. Outside it's a dead ringer for London's Buckingham Palace. Inside, the tour route passes through four grandly decorated rooms – the most impressive being the Kacho-no-Ma (Room of Flowers and Birds), with Japanese ash panels inset with cloisonné panels – plus the entrance hall and main staircase.
Japan's only neo-baroque European-style palace was designed by Katayama Tōkuma, a pupil of British architect Josiah Conder, and completed in 1909. During its lifetime it's hardly been used by the imperial family and today serves duty as the State Guest House, providing accommodation and a diplomatic meeting space for visiting heads of state and other VIPs.
If you haven't reserved an entry ticket online (which you will need to do around two months in advance), head to the front gate to get one of the timed entry tickets, which are made available from 8am. It's very popular with locals so you may have to wait anything up to an hour to get in when your time slot comes up.
Online reservation is essential for 10 daily guided tours (lasting 30 minutes) around Yushin-Tei, the Japanese-style annex building in a separate part of the grounds; the 3pm tour (the last of the day) is in English. The cost of this tour plus entry to the main palace for an adult is ¥2000.