But we'd also be without some of the most gigantic, mind-boggling works of art the planet has ever known. Is any of the stuff on this list particularly useful? Nope. Is it all impressive? Absolutely.

Where would the world be without the efforts of lone, obsessed people with lots of time on their hands? Well, we'd be without most of the world's great inventions, books, political movements and religions, for one thing.

5 Madrid's Cathedral of Trash

Citynoise.org

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What could motivate a man to spend 50 years building his own cathedral out of garbage? Is there any reasonable answer to that? And we're talking life-size here.

It's the work of Spanish monk Justo Gallego Martinez, who had a personal crisis in 1961, when he contracted tuberculosis and then got kicked out of the monastery. So he started building. What Don Justo lacked in blueprints, engineering knowledge, building permits and forethought, he made up for in enthusiasm. Thanks to local donations and daily visits to brick factory yards, Don Justo accumulated enough materials to build a church standing 131 feet tall.

Dubasdey via HuffPost

It doesn't even need God to smite sinners. Just a stiff breeze.

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The church features cupolas made of plastic food tubs, columns made of oil drums and towers that are nothing more than stacked paint buckets. Don Justo works without a crane or crew, and no one wants to even know what's going on with the foundation or bracing of the building (he'll legally never be able to allow worshipers inside, for fear of creating an extremely tragic headline the next day). So far, the city council -- and gravity -- have decided to turn a blind eye, both out of respect for his convictions and because of the tourists he attracts.