Union square is a big shopping mall with shops (obviously), cafes, lots of chain restaurants (Zizzi, Wagamamas, Yo Sushi, TGIs, Nandos etc.) and a big cinema. It is a good place to go if you are looking for somewhere to spend an evening. We went to see the new F1 film Rush this evening - such a good film! Definitely worth a watch if you haven't seen it yet. With Chris Hemsworth and Olivia Wilde there isn't much that could go wrong!
Also, definitely try the ice cream sundaes in Handmade Burger if you want a post-film snack.. heaven in a dessert!