Solo, Franciscan Monastery & Old Pharmacy works.
The genuine curiosity is the pharmacy: operating since 1317, it's among the oldest still-working pharmacies in Europe, with original apothecary jars and recipe books behind the counter where you can still fill a prescription. The Romanesque cloister off the busy Stradun is a shaded breath of calm. The honest catch is that it's the busier, Pile-side monastery and the data's own verdict is that the Dominican has the better cloister — so if you're only doing one for the architecture, this is the one to skip; come here specifically for the 700-year-old pharmacy.