Emperor of Japan's main residence, built on the former Edo Castle site — a massive feudal stronghold that burned down in stages through the 19th century. The East Gardens are open 9am daily and free to walk. The palace itself requires a guided-tour booking online for inner-ground access. In sakura season, rent a rowboat on the Chidorigafuchi moat for 400 yen — famously one of Tokyo's best cherry blossom spots.