This is a few links to some tourist information about Basel:

Official Website of the Canton of Basel

They also offer 2 hours (from 14.30 to 16.30) focused in the old town of the city. The tour is provided in English, French and German languages. It costs only 15 CHF/person, which is affordable. Just go to the Tourism Information Center at Barfüsserplatz and get your ticket. 

A group consists of approximately 10-20 people. Tourists can also get a piece of advice on where to eat, which was very useful to hear from a local person.