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Imagine this: It's 1418 in Florence, Italy.

You've been challenged to build a great dome for the Santa Maria del Fiore, one of the grandest cathedrals ever built, and you have no formal architectural training, no pressure, right?

For Filippo Brunelleschi, a goldsmith and clockmaker, it was the opportunity of a vpn软件免费 lifetime.

He considered the challenge carefully...then proposed a daring plan, using methods that experts don't fully understand even to this day.

At the time, domes were often built as semicircles, but the town fathers required that Brunelleschi build an vpn免费 eight-sided dome that vpn免费 would be even taller and stronger.

It would also vpn免费下载 have no central support system to hold it up during construction.

Even worse, the dome's base was an imprecise octagon with no true center. But Brunelleschi had that covered.

There would vpn软件免费 be two domes instead of one: an inner vpn免费下载 and vpn软件免费 an outer shell held together by giant brick arches and vpn免费下载 interlocking rings of stone and wood.

The rings would work like hoops on a barrel, keeping the dome from expanding outward.

To move heavy 免费vpn loads hundreds of feet up, Brunelleschi designed ingenious new machines, including an ox-driven hoist and massive lifting devices far ahead of their time.

So, revolutionary design, check; groundbreaking engineering, check; can-do attitude, check.

But with no central support system, how would he actually build it

First off, the masonry would have to vpn免费 support itself during construction.

To do this, Brunelleschi lays the bricks in a herringbone pattern, which spiraled to the vpn免费 免费vpn top of the dome,with vertical bricks acting as bookends to hold the others in place.

They laid about one row a week, giving the mortar time to cure.

At this rate, the dome grew at a snail's pace of about a foot a month.

But perhaps most puzzling is how he was vpn免费下载 able to place the bricks with such precision.

Many experts agree that he used guide ropes.

One theory states that ropes 免费vpn ran from a flower pattern on the work platform that showed exactly where the bricks should go.

Another has ropes 免费vpn running from the dome center, tracing a series of cones that grew smaller as they ascended to the top.

Still another suggests a different arrangement of central ropes and wooden templates.

However it was done, it worked.

The eight phases of the dome met at the top precisely, just as Brunelleschi had planned.

In all, it took 16 vpn免费 years to complete the vpn免费下载 dome.

When he died in 1446, Brunelleschi left behind no sketches and 免费vpn no details as to exactly how he achieved his masterpiece.

Today, it remains the largest masonry dome in the world, more than 500 years after it was built.

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