Act 3 of Baldur's Gate 3 opens with players on the outskirts of the titular city, Baldur's Gate. Unfortunately, while there's plenty to do in Rivington, a massive fortification bars the way to the city itself: Wyrm's Rock Fortress.
Baldur's Gate 3: How To Get Into The Main City
Wyrm's Rock Fortress is a major obstacle between players and Baldur's Gate, but there are many ways to surmount it.