For ten weeks each summer, the doors of the most famous address in Britain swing open. Tour the 19 State Rooms used by the King to host visiting heads of state, the Throne Room, the Ballroom, the Grand Staircase, the White Drawing Room all dressed with treasures from the Royal Collection (think Rembrandt, Vermeer, Canaletto). Step out into the 39-acre garden, and finish with afternoon tea on the lawn.