The world is full of strange buildings and artifacts - both manmade and natural - that baffle those who encounter them. Some are strange due to their structure, others because of our inability to decipher their intended meaning.
One excellent example of this is the Georgia Guidestones in Elberton. Commissioned in 1979 by a man whose identity was purposefully kept a secret, the "American Stonehenge" contains supposed advice for rebuilding civilization after the end of the world.
The granite architecture still stands in Georgia today, but even after decades, seemingly no one understands who's really behind the Guidestones, what their purpose is, or why they exist at all.