Walk along the banks of the Rhine river
Start from the Parliament and reach the port area along the Rheinuferpromenade, the promenade that runs along the Rhine. In this pedestrianized promenade you will find groups of young people lying on the grass, cyclists and people on foot. Join them, it's really nice and relaxing to spend a few hours here. Along the way, you will notice many places of interest such as the church of San Lambert and Burgplatz, with the world-famous Schlossturm. If you're tired of walking and want to take a break, wherever you are you'll find bars and patisseries just around the corner.
In summer, a boat tour of the Rhine is worthwhile. The ride lasts 45 minutes and you can choose between different shipping companies, some even offer the "all-you-can-drink" formula.