The old observatory in Tartu sits on Toome Hill, a leafy mound in the middle of the town beside the river Emajõgi, and it was once one of the most important scientific instruments in the world. The university was founded in 1632 by the Swedish king Gustavus Adolphus, and the town was then known by its German name Dorpat. In the early nineteenth century the astronomer Friedrich Georg Wilhelm Struve built the observatory here, equipped with a remarkable refractor made by Joseph von Fraunhofer in Munich, which was the best telescope of its day. Struve used it to measure double stars, and he also led a great surveying project that ran a chain of triangulation points from the Arctic Ocean to the Black Sea.
The chain, now known as the Struve Geodetic Arc, was created to measure the size and shape of the Earth, and it was one of the first reliable measurements of that kind. UNESCO listed it in 2005, with points in ten countries, and the observatory is one of the Estonian sites. The neoclassical building, painted in soft yellow, is now a museum, and the grounds around it are a pleasant park with views toward the rooftops and the church towers. The hill also has the ruins of the cathedral, a vast medieval brick shell where the university library was later housed.
Tartu is a lively student city of about a hundred thousand people, and its streets are full of bicycles and cafes in the old wooden houses. Riding in is easy, with a good surface and clear signs, and traffic is moderate. Parking a motorbike near the hill is usually straightforward, but cobbled lanes call for care in rain. The surrounding country is gentle, with fields, birch woods and lakes, and the roads outside the town are quiet and well kept. Be ready for gravel on minor roads in the countryside.
Fuel stations are plentiful on the edges of town, and the centre has a large choice of places to eat, from simple Estonian dishes to student-friendly cafes. The air on the hill smells of lime trees in early summer and fallen leaves in autumn. The stones of the old observatory are a good place to pause: in a small, quiet room beneath its dome, a very big idea about the shape of the planet once began.