国外媒体:神秘的阿卡帕纳金字塔（在线收听）

阿卡帕纳是最大的梯形金字塔，曾被认为是一座人工堆建的小山。阿卡帕纳金字塔是遗址中最大的建筑，塔底平面呈长方形，长180米，140米。

One thousand years before Columbus, they were pyramid builders, warriors, the architects of an empire in South America. The Tiwanaku lived in a valley of Lake Titicaca for 1,500 hundred years. And then their civilization vanished, leaving behind only stone ruins and the enduring mystery of their passing.

The center piece of Tiwanaku's spiritual power was the Akapana Pyramid, surrounding the pyramid, cities and temples, was a vast maze of channels and regions, though they look like irrigation ditches, they were far too complex.

The mystery of their purpose is one that archaeologist Alan Kolata  had been struggling to solve. Kolata had a hunch, and to prove it he asked the local farmer to plant crops along the channel banks. Then the archaeologist and the farmers led in the water. Crops spouted and began to grow. But then a tremendous frost hit the outer planter. It devastated other fields, but the crops landed along the canals were not affected.

The key to the sophistication of these, uh, of these raise fill system are really these canals that you see here all around me. What's important about the maze is they function like gigantic solar collectors.

If you fetch this water you'll see that it's warm enough to bay, and it's truly remarkable and here we are up at 14,000 feet. And that's really the key to the system. It really prevents frost from damaging the crops that would be growing up on these field platform services here.

The mystery was solved. The Tiwanaku had found a way to control the environment of the valley itself. Their canals store heat during the day, then radiate it over the fields at night. This remarkable system provided the wealth to build an empire, and to keep it for over a millennium. But then a mid-growing political turmoil, the empire began to decline.

For the Tiwanaku, it was the end, but for the local farmers, it is a new beginning. Secure from the frost, the raise fields proved to be seven times more productive, providing hope for a better harvest, and pride for their ancestor wisdom that is returned from the past.