As it’s in Baden Wurttemberg a BW ticket would suffice .
Schedule of trains
Check for the schedule of trains from Stuttgart to Blaubeuren. The basic BW tickets allows only second class travel. First class travel can be availed for a small extra fee. Please check DB website here. Most of the connection require you to get off at the Ulm and catch the second train to Blaubeuren. From Blaubeuren station Blautopf is a 20 minutes walk. Take the Karlstrasse right in front of the station followed by the Klosterstrasse. Take a right where the Klosterstrasse meets Lindenstrasse. After a few metres you will be at the Blautopf.
What to do there
If you are into trekking or extreme bicycling there are some trekking routes here. If you just want to relax then one can sit beside the beautiful spring. There are restaurants around the place as well. We found it an ideal place to spend an afternoon there.