The Kanton Basel actually does not exist, there are two so-called half-Cantons called Basel-Stadt (Basel City) and Basel-Landschaft (Basel County). The city of Basel has no underground sights so all the listing are actually in Basel-Landschaft, but this page is actually for both. Basel is close to the German border at the Rhine, the whole area is lowland, a little hilly and German speaking. Basel is famous for its industry, mostly chemical and pharmacy. Its also infamous, as one of those companies used a pollution event in the 1980s to get rid of their own poisonous waste by releasing it into the Rhine hoping the main event would cover this. After chemical analysis had proven their guilt, they said "Oops, that was an accident!". Actually a public relation desaster. As a result numerous laws were changed and the supervision intensified, and today the Rhine is almost unpolluted again, and even salmons have returned.
The hills are mostly made of Mesozoic sedimentary rocks covered by glacial remains. There is karst and caves, but the caves are rather small and there are no show caves. But there is a very interesting karst trails with numerous small caves. The salt mining in the area is based on a layer of evaporitic salt which is not mined, but dissolved with water and pumped out as brine..