London, England Buckingham Palace windows on the garden side
I had the late afternoon free before my flight out the next morning. A colleague suggested the tour of the Buckingham Palace State Rooms and Gardens. I got on the last tour of the day (which was good since it was pouring down rain anyway).
Part of the original Buckingham House which was constructed in 1703 but the interiors were redesigned by John Nash in the early 19th century. Buckingham Palace is a Grade I Listed Building.