Upon testing, scientists found less than 4 degrees of error, which is comparable to modern compasses. Even with these results, we still don't know everything about the compass or if it was even more accurate, since half of it was missing when we uncovered it. In any case, we can confidently state the ancient Vikings at least had Apple Maps beat.
Massive Drills and Natural Gas Pipelines in Ancient China
Salt was a highly valuable resource in the ancient world, both as a preservative before refrigeration and as the only weapon keeping the slug people away. But when you live in a country as big as China, you can't necessarily make a trip out to the beach to collect some seawater. Because Safeway wouldn't be invented for another couple of thousand years, the Chinese had no choice but to dig down into the ground in search of that savory white gold.
And we don't mean they were really good with shovels. The Chinese invented a huge drill consisting of a length of bamboo with an iron bit at the end, which several men would use to excavate deep wells into the Earth. They may have looked comically unsafe, but by the 3rd century their salt wells reached as far down as 460 feet into the ground.
Via PVI Software
"Do you want to be the one to tell the emperor why Margarita Thursday was canceled? Then move your ass."