Located in the emblematic Karlsplatz, in the heart of Vienna, you'll find Karlskirche, one of Vienna's icons. The best way to get there is by metro. Get off at the Karlsplatz top or tram 71. The entry fee to the temple is 6 euros. It was built by Charles the 6th upon the end of the plague in 1713. The two columns flanking the entrance are 33 meters high and decorated with motifs from Saint Charles's life. The visit includes going up to the dome from which you'll have a beautiful panorama of the city.
At night it's lighted until about midnight and it's possible to take some great night photos.