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In page Samarkand:

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Between 1424 and 1429, the great astronomer Ulugh Beg built the Samarkand Observatory. The sextant was 11 metres long and once rose to the top of the surrounding three-storey structure, although it was kept underground to protect it from earthquakes. Calibrated along its length, it was the world's largest 90-degree quadrant at the time.[7] However, the observatory was destroyed by religious fanatics in 1449.[7][8]