Built as part of Tartu University in 1810, this intriguing observatory on Toomemägi is a must for fans of astronomy and the history of scientific discovery. The sober, studious-looking facility, topped with a moving observational tower, houses some of the most famous artefacts of 19th-century astronomy, all displayed in perfect order. You can climb the tower, where a huge Zeiss Refractor remains in place; there's a basement exhibition on seismology; and interactive-learning displays await in the Western Hall.
Tartu was for many years one of the world's leading observatories. Its first luminary, Friedrich Georg Wilhelm Struve, installed the 9-inch Fraunhofer Refractor, then the world's largest telescope, here, plus other cutting-edge instruments with which he (amongst other things): measured the Struve Geodetic Arc that allowed accurate measurements of the earth; discovered over 3000 stars; and was the first person to measure the distance to a particular star. The Refractor, all gleaming brass, polished wood and immaculate engineering, is just one of many beautiful and significant instruments here on display. You can also see Struve's Geodetic Arc measurements, less visually-arresting, but listed by Unesco for their immense contribution to human knowledge.