I would have to say that Buckingham Palace (formerly known as Buckingham House) is probably the most famous place in London - UK. But, unless you are someone famous, a hero, or a visiting head of state, you won't see much of the interior of the Palace. It can only be toured from 9:30am - 4:30pm in the months of August & September and then only the State Rooms!
The public entrance to the palace is through the Ambassador's Court. I was in London in January, so I could only see it from afar. The literature that I read said that the palace has 600 rooms and that it is surrounded by 45 acres of gardens. For me, the good news was that I was able to see up close the Victoria Monument outside the palace, and what a glorious monument it is! It's huge, the largest monument dedicated to any king or queen in London.
Edward VII planned this memorial for his mother, Queen Victoria. The designer, Edward Webb, used 2300 tons of marble, and the project took five years to complete. How sad that Edward VII did not live to see it completed. The Victoria Memorial is located at the west end of the Mall. Note: You are able to see the CHANGING OF THE QUEEN'S GUARD during May through August daily at 11:30 am. During September through April, it happens on alternate days & is subject to change without notice.