Lviv's Jesuit Church was built between 1610 and 1630 on the model of Il Gesu in Rome, giving the old town one of its grandest Baroque interiors. It was large enough to hold thousands of worshippers and later became tied to civic history, including meetings of Galicia's provincial parliament.
The underground rooms are a good reason to stop rather than simply admire the facade. Go with a guide if one is available, as the layers beneath the church explain a lot about Lviv's religious and political past.