São Julião is the oldest parish church in Setúbal, founded in the 13th century and rebuilt several times after earthquakes — most disastrously in 1755, when the Lisbon quake took down most of the medieval structure. The current building dates largely from the 18th century but preserves a fine Manueline side portal from the original.
Inside, gilded baroque altarpieces and 17th-century azulejo panels of the life of Saint Julian cover the walls. It's a working parish church on a busy street, so come during opening hours and expect to share the space with the occasional candle-lighting local.