Astronomical Observing Sites Planetario Ulrico Hoepli In 1929 Ulrico Hoepli donated the Planetarium to the City of Milan, which opened it to the public the following year. The construction is in neoclassical style, wanted by the architect Piero Portaluppi. The Planetarium has the dome completely covered with a cloth on which the starry sky is projected. It is the most visited planetarium in Italy and often hosts cultural events and conferences.