The metro Vienna is the fastest and easiest public transportation in the city. In the center you can find also a high density of metro stations. In the City Center Map from city-walks you can find all the stations in downtown. A single trip within the center costs approx. 2,40 Euro. A day ticket on site costs from approx. 8,00 Euro (24h Ticket for the whole city area).
If you are a tourist and stay for at least 2 days you should buy the Vienna City Card starting from approx. 25,00 Euro. With this card you can use the metro and you get numerous discounts to different sights, attractions and museums. The trains are running on workdays from approx. 5:00 morning to approx. 24:00 o'clock in the night. On Saturdays, Sundays and public holidays the trains are running 24 hours. The metro Vienna cycle times are varying from 5 minutes during the day to 15 minutes at night-time.