4. The Flower Dome at Gardens by the Bay in Singapore
This beauty is the world's tallest columnless greenhouse; its glass sits on a steel grid that acts like an eggshell. Like a giant, beautiful puzzle, there are 3,332 glass panels in a variety of sizes and shapes. Air is cooled at the lower zones through pipes, while the warm air is vented out the top.
The Flower Dome has an ever-changing display of flowers from all over the world, including ancient olive trees that are estimated to be more than 10,000 years old!
© John Harper/Corbis