4. Helix Bridge

If you've ever been to Singapore, you'll know that the city-state goes to great lengths to make public infrastructure beautiful. They have, for instance, the most inventive airport in the world. It's also home to some of the world's coolest bridges -- like the Helix. As the name suggests, it's enmeshed in metallic spirals designed to mimic the shape of human DNA. It even has C, G, A and T letters that light up at night, signifying the four chemical bases of DNA.