Borough Market is a big food market where you can find wide variety of selections literally from all around the world. In addition it is nice to taste different ingredients and foods prepared on the stands. From Spanish Chorizo to Turkish delight to Specialty Cheeses it is a heavenly place to experience different cuisines. The market is open on saturdays. Be informed that the place gets very crowded.
If you are nearby It might be a good idea to have a short walk towards Waterloo. On your way, you will come across some important landmarks; such as Anchor (a historic pub), Oxo Tower, Tate Modern Museum, London Eye or Royal Festival Hall.
Borough Market is definitely a must see place in London to fully grasp the cultural richness and diversity of London.