As with the Naschmarkt, Karlsplatz was formed when the River Wien was covered over at the turn of the 20th century. At the time, architect Otto Wagner expressed his frustration with the result—too large a space for a formal square and too small a space for an informal park—and the awkwardness is felt to this day. The buildings surrounding the Karlsplatz, however, are quite sure of themselves: the area is dominated by the classic Karlskirche, made less dramatic by the unfortunate reflecting pool with its Henry Moore sculpture, wholly out of place, in front. On the south side of the Resselpark, that part of Karlsplatz named for the inventor of the screw propeller for ships, stands the Technical University (1816–18). In a house that occupied the space closest to the church, Italian composer Antonio Vivaldi died in 1741; a plaque marks the spot. On the north side, across the heavily traveled roadway, are the Künstlerhaus (built in 1881 and still in use as an exhibition hall) and the Musikverein. The latter, finished in 1869, is now home to the Vienna Philharmonic. The downstairs lobby and the two halls upstairs have been restored and glow with fresh gilding. The main hall has what may be the world's finest acoustics.
Some of Wagner's finest Secessionist work can be seen two blocks east on the northern edge of Karlsplatz. In 1893 Wagner was appointed architectural supervisor of the new Vienna City Railway, and the matched pair of small pavilions he designed, the Otto Wagner Stadtbahn Pavilions, at No. 1 Karlsplatz, in 1898 are among the city's most ingratiating buildings. Their structural framework is frankly exposed (in keeping with Wagner's belief in architectural honesty), but they are also lovingly decorated (in keeping with the Viennese fondness for architectural finery). The result is Jugendstil at its very best, melding plain and fancy with grace and insouciance.