I would like to talk all about pyramids, and not just the Egyptian ones. Some interesting notes:

1. Pyramids have been found in the Atlantic Ocean
2. ...and off the coast of Japan...
3. ...and several in China.

The descriptions make them sound very similar in structure. It's funny that China has denied having any pyramids until recently. You can Google Earth them and see them for yourself.

Chinese Pyramids coordinates (copied from World-Mysteries.com):

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Maoling Mausoleum 1: size 222 x 217 m, 34°20'17"N 108°34'11"E
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Pyramid 6: size 153 x 158 m, 34°21'47.16"N 108°37'49.80"E
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Pyramid 7: size 149 x 155 m, 34°21'42.48"N 108°38'24.36"E
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Pyramid 11: size 155 x 154 m, 34°22'29.64"N 108°41'51.36"E
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Pyramid 15: size 219 x 230 m, 34°23'52"N 108°42'43"E
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Pyramid 31: size 126 x 149 m, 34°14'09.00"N 109°07'05.00"E
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Pyramids 33,34,35: bigest 160 x 167 m, 34°10'45.00"N 109°01'41.00"E
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Huang-ti Mausoleum 37: size 354 x 357 m, 34°22'52"N 109°15'12"E


As for the underwater pyramids, there have been some strange claims. One diving team claimed that they came upon a pyramid in the depths of the ocean, and there was a crystal (capstone I think it was) that shone so bright it lit the surrounding dark water.

I would like to think that the pyramids are architecture left from the Atlanteans, seeing as the Greek talked about Atlantis when visiting Egypt, who's priests talked of the details. I'm not sure the connection to China though.

Keep in mind, all these details I've only read about, so can only speculate on.