Designed by John Nash in 1830, Trafalgar Square is the largest square in London. With all the cultural events taking place here, including demonstrations and New Year's Eve celebrations, it is often considered the heart of the city.
Nelson's Column stands in the center of the square with four lion statues around. It was built in 1843 to commemorate Admiral Nelson. The lions are a popular selfie spot with tourists often climbing them.
When at the Trafalgar Square, consider visiting the National Gallery. Its main entrance is located at the Trafalgar Square and you can see many artworks by renowned artists (e.g. Da Vinci) there. The entrance is free so it is a good place to visit for those traveling on a budget.