Ulugh Beg Observatory
Remains of a 1420s observatory with the underground arc of its sextant.
A giant sextant
The main instrument of the observatory, built in the 1420s, was a huge Fakhri sextant with a radius of about 40 metres, the largest of its kind at the time.
Sources: https://mathshistory.st-andrews.ac.uk/DSB/Ulugh_Beg.pdf
Found in 1908
For centuries no one knew where the observatory had stood. In 1908 the archaeologist Vasily Vyatkin found its remains and uncovered the underground part of the marble arc, which can still be seen.
Sources: https://mathshistory.st-andrews.ac.uk/DSB/Ulugh_Beg.pdf, https://archnet.org/sites/2465
The star catalogue
Ulugh Beg's catalogue listed 1,018 stars.
Sources: https://mathshistory.st-andrews.ac.uk/DSB/Ulugh_Beg.pdf
The fate of a scholar ruler
Ulugh Beg was Timur's grandson, a ruler and an astronomer. In 1449 he was put to death at the instigation of his own son, Abd al-Latif.
Sources: https://www.britannica.com/biography/Ulugh-Beg