On our way back from Buckingham Palace, we cut through Green Park. I spent a lot of time commuting through Green Park station so it was nice to be up above and in the lovely, green park. I thought this arch at the end was Marble Arch, but I was mistaken, and for a small fee, you can go up Wellington Arch, which also gives you a lovely view over the city and the park. It was a super clear day, so you could see quite a lot too! It was nice random thing to discover!