The origin of the Astronomical Observatory of Trieste dates from 1753 when the Austrian Empress Maria Theresia established here the Nautical School. For some decades it was hosted in the Jesuit College of Santa Maria Maggiore. Astronomy was a curricular subject taught to future captains. In 1817 the Nautical School became the Academy for Commerce and Navigation and was moved to Palazzo Biserino, located on today's Piazza Hortis. In 1851 an Astronomical Observatory was installed on the roof and in 1898 it became autonomous from the Academy. The director was F. Anton and the seat was moved to the town periphery to a new and big building with the aspect of a medieval palace (castello Basevi), which still hosts the Observatory. Under the direction of E. Mazelle the most modern instrumentation for astronomy, seismology and meteorology available at the time was acquired, such as the meridian circle of Troughton & Simms. In 1904 the Reinfelder refractor telescope was installed in the newly built dome of the neoclassical pavilion in the park of Basevi castle. With this instrument, J. Krieger compiled his Moon Atlas. Annexed to the Kingdom of Italy, In 1925 the Institute was equipped with a new Zeiss 50 cm reflecting telescope. For several years only a few observations were possible due to the light pollution of the town. In September 1944 the Observatory was bombed. After the war the Observatory was reconstructed and made fully operational again. Astronomers started novel research programs in the field of photoelectric photometry. The growth of the Observatory continued after 1964 through the great increase of both research activities and staff by the new director, M. Hack. A new observing station was built in Basovizza on the Carso Plateau where new telescopes were installed. In 1999 the Observatory became part of the National Institute for Astrophysics (INAF).

The Astronomical Observatory of Trieste (OATs) is currently one of the 17 research institutes that form the National Institute for Astrophysics (INAF). OATs has a long history and, starting over 50 years ago, its contribution to research started to be internationally recognized. The historic building that first hosted OATs is Castello Basevi, which is not far from S. Giusto hill. Over the years, first the observing station of Basovizza, on the Trieste Karst, and then Villa Bazzoni, on S.Vito hill, were added to Castello Basevi headquarters. The observing station at Basovizza hosts instrumentations and laboratories, and is also open to public visits. Villa Bazzoni also hosts the astrophysical staff of the Physics Department of Trieste University. Research activities performed at OATs are on cosmology, clusters of galaxies, stellar and galactic evolution, solar and planetary physics, high energy physics, and astrobiology. Besides scientific research, innovative technologies are being developed and employed for the exploration of the universe from the ground and from the space. All research performed at OATs is supported by a broad network of national and international collaborations. Among them, the most important in terms of observations and technology are the cooperation with ESA, European Space Agency, and with ESO, European Southern Observatory. In the last years, OATs has participated in over than 25 European and international projects. An average of 170 scientific papers and 40 scientific and outreach events are, respectively, published and organized, each year. OATs is also devoted to training in physics, offering teaching activities at undergraduate and graduate levels of Trieste University and SISSA (International School of Advanced Studies), as well as funding study and research fellowships. OATs also carries out intense outreach activities in its Basovizza branch, which hosts various telescopes as well as an interactive laboratory, and is visited by thousands of people each year.