Buckingham Palace

The official ‘office’ of H.M. Queen Elizabeth II of the United Kingdom. She may reside and work in Windsor Castle, but the palace remains the symbol of the British monarchy, representing many special events and important traditions. Additionally, changing the guard does attract many visitors each time. 

Do know, important events and ceremonies attract many visitors. If you plan to attend one, plan ahead, both the way to the event and the time you should be there in advance.)

(Please check the official calendar for the concerning dates, as it does not take place every day. 
https://www.householddivision.org.uk/changing-the-guard-calendar.)