Covering 93 square kilometers of wetland in Vienna and Lower Austria, the National Park Donau Auen was established in 1996 and is an important habitat for many different species of mammals, birds, and plants. More than 100 different species of birds can be spotted in the park, making it an excellent destination for birdwatchers, but other popular activities here include kayaking, horseback riding, bicycling, and hiking. Guided tours are available, but a network of clearly marked trails makes it easy to explore on your own. Visitors can also take boat trips from Salztorbrücke; these last approximately 4.5 hours and must be reserved in advance.