Buildings may be some of the most impressive works of art we have.
After untold sums of money are sunk into their construction, we can walk through the finished products and even live inside them. Older structures offer a window into the past, while newer buildings provide a sense of where we're headed.
Here are some of the most ambitious projects from architects around the world, whose works span thousands of years.
The oldest building we know of, built around 9500 B.C., is Gobekli Tepe in present-day Turkey. Archaeologists aren't certain of its function, but it was probably religious.
Since then, humans have built some pretty rad structures. In the past year, we've seen futuristic openings like the Fulton Center in New York ...
... and the Penleigh and Essendon Grammar School in Melbourne, Australia.
The Golden Temple in Amritsar, India, is a stunning structure surrounded by a massive pool. It is the center of the Sikh faith, and it's lustrous at night.
The Las Lajas Sanctuary in Narino, Colombia, is equally mystifying. It looks as if it defies gravity.
The modernist architect Antoni Gaudí didn't live to see his Sagrada Família completed — in fact, it's still being built. The exterior looks like something out of Narnia ...
... and the interior is even more surreal.
In nearby Portugal, the Belém Tower has dungeons that once served as prisons. It's one of the best examples of Portuguese gothic architecture.