You can't come to London without a royal encounter, so be sure to catch the changing of the guard ceremony at Buckingham Palace for free. The changing guard takes place throughout the year - check the exact time ahead of your visit.
Or, take a stroll through Kensington Gardens, one of the city's Royal Parks. Here, you'll discover a peaceful slice of London in the Italian Gardens, or by browsing the latest exhibition at the Serpentine Galleries.
It doesn't cost a penny to wander London's cosmopolitan and eclectic markets - although you will need immense willpower not to get your wallet out. The diverse range of street markets dotted across the city offers a glimpse of the amazing food, antiques and crafts available locally.
A walk through the Caribbean cuisine of Brixton Market, or the thriving, foodies' heaven of Borough Market - whose traders sell produce from all corners of the globe - is sure to set your stomach rumbling.
Portobello Road Market, famous for its antiques stalls on Saturdays, is a mile-long stretch of shops and alleyways packed with vendors and bargain hunters.
The vibrant Brick Lane Market, where funky furniture and unusual wares are in ample supply, is best visited on Sundays.