Generally speaking, 2-3 days in Basel should suffice for most visitors. During this time, you'll have the chance to explore the charming Old Town with its historic landmarks and architectural gems, including the iconic red sandstone Münster cathedral and the medieval Gate of Spalen. You can also wander through the bustling Marktplatz (marketplace) where locals sell fresh produce and artisanal goods or along the picturesque Rhine promenade with its stunning views of the river and surrounding hills.
Two or three days is also enough time to visit some of Basel's world-renowned museums such as the Kunstmuseum Basel, Fondation Beyeler or the Vitra Design Museum.