If you're interested in baroque churches, this is a great opportunity to see two great examples within 100m of each other. The main cathedral, St. Ursen, can't be missed. It towers over the Hauptgasse and pretty much over the whole Altstadt (old town). I don't know very much about baroque styles, but it's a neat change from the usual Gothic churches that one comes across in this part of Europe. The smaller Jesuit church is almost hidden. Walk down the Hauptgasse from St. Ursen and you'll see the doors on your left. Stepping inside feels almost like stepping inside a secret world. From the outside, you probably wouldn't suspect the little treasure of a church inside.
From journal The Afternoon in Solothurn