Teatro Lavalleja is the town theatre, a handsome early-20th-century building that still carries Minas' old civic confidence. Its facade is the main reason to seek it out if there is no performance on, but the building also anchors the cultural life of the centre.
Check local listings if you are staying overnight; small-town theatres in Uruguay often host concerts, school productions, and touring shows that give a better feel for the place than another cafe stop.