The Vienna Prater is both a huge outdoor area and an amusement park. Once the Emperor Maximilian II's hunting ground in the 16th century, in 1766 Emperor Joseph II declared it open parkland for everyone. Coffee-houses and cafes sprang up and nobody seemed worried that it continued to be used for hunting until 1920! It was also around the 18th century that the Wurstelprater began - an amusement park which continues to this day and includes the giant ferris wheel, the Riesenrad, one of Vienna's famous sights. There are also bumper cars, a roller-coaster, and carousels.
The Prater also houses a planetarium and the Prater Museum, a little disappointing as museums go although the antique slot machines are worthwhile.
Well worth the effort but I'd advised to start at the Zoo no later than 0930hrs and spend at least 6 hours wandering around the Zoo and then go onto Ferris Wheel making sure you get a copy of both Zoo and Ferris Wheel Voucher otherwise you have to pay again when you arrive at the Prater and go on the Ferris Wheel. Spectacular views of the city from wheel so I'd suggest doing this at night time or even do 2 trips on the wheel -- 1 Day and 1 Night. Can have special meal in one of the carriages of the Giant Ferris Wheel. Would be ideal if celebrating something special whilst in Venna. Make sure you have enough memory cards for your camera so you can take as many phots as you like on any of the tours.
Both the Zoo and the Prater are fairly empty in Winter. If you want to take photos at the zoo, it was easier this time of year than I imagine it would be in the summer. Most of the rides at the Prater were not running, but a few were, which was ok, because we mostly just wanted to walk around and take pictures. The woman working the ticket desk at the zoo was confused when we presented our vouchers, but they figured it out. I highly recommend both the zoo and the Prater!
Catch U1 to Praterstern.