Karlsplatz is the buisiest square of the city, and the intersection station for the three main underground lines U1, U2 and U4, as well as many other tramways and busses of Wiener Linien , Vienna Public Transport. The Jugendstilpavillions designed by architect Otto Wagner for the suburban railway, another Viennese jugendstil building: the Secession, Church of St. Charles Borromeo - Karlzkirche , main buildings of the Technical University of Vienna, Concert Halls - Musikverinsgebäude, the Vienna Museum and Resselpark are the places that you should visit in Karlsplatz during your stay in Vienna.