From the Black Forest, the Donau (Danube) begins a journey of 2902 kilometers, which takes its waters through 10 different States and ends in the Black Sea. It is the largest navigable river which runs through major EU capitals and small towns: Ulm is one of them. The presence of the river characterizes the settlement, creating a natural boundary with the more modern twin, the Neu-Ulm and then with Bavaria; while in the course of history Danube was the key to the economic success of the city, allowing its development to a thriving commercial center since the sixteenth century. The defensive walls, built right in the midst of its waters in 1480, offer a scenic walk today. The ditches behind the walls have been transformed into gardens and orchards. The Metzgerturm (The Tower of the Butchers) from 1349 or so, with its slope of 2.05 meters is the gate of the promenade along the river banks. Cycling and walking paths were created along the river throughout its length and there are so many people who have chosen its banks as a place for sport and relaxation. Swans, ducks and ducklings float peacefully approaching the shore when lured by a morsel of dry bread offered by some child. The Park of Friedrichsau, north east from the center, also overlooks the Danube, a public park since 1811. There is an excellent variety of options to spend a day outdoors: you can choose between trees and ponds, the space for docking the boats, playground, miniature golf field, island events, beer gardens and taverns. In the heart of the park lies the zoo, the aquarium and a tropical greenhouse: here you can admire a variety of fish, amphibians, reptiles, birds, insects and mammals, all housed in 95 individual structures. A particularly loved attraction is the cave of the bears with free access to an observation terrace. For the small ones, there are places where they can caress the animals - an event not to be missed.