The Astronomical Bastion (also referred to as the Observatory Bastion) was built in 1862 as part of the major Prussian re-fortification of the city in the mid-19th century. It was located in close proximity to the illustrious observatory of Königsberg University, where celebrated astronomer Friedrich Wilhelm Bessel charted tens of thousands of stars. Although not particularly visible today as a result of modern urban development, the observatory was situated on raised ground of great strategic value, thus making it the perfect place to situate a new defensive structure. In August 1944, an RAF air raid obliterated the observatory but the bastion was still able to be utilised by the defending German troops and it was allegedly one of the last positions to fall when the Red Army swept into the city in April 1945. Although currently closed to the public, it is possible to walk right around the structure and you might even get a glimpse over the walls from a suitable vantage point.
While Königsberg as a whole suffered untold devastation, the observatory was a particularly notable loss. Commissioned by King Friedrich Wilhelm III of Prussia at the beginning of the 19th century when the entire university had just 332 students on its books, the investment paid off quickly as Bessel, who became its first director in 1810 and began publishing his groundbreaking findings in 1812, helped to establish it (together with F.W. Argelander and Artur Auwers) as a new and significant centre of scientific discovery.