The Forgotten Realms has many planes of existence and settings within those planes. One of the settings that hasn't received as much attention in 5e is the Underdark, a massive network of subterranean caves and passages that house a multitude of races, flora, and fauna. While 5e has passed over the Underdark in recent years, Baldur's Gate 3 turned the Underdark into a marvel, where exploration of it felt like venturing into an alien world. The Underdark is encountered in Act 1 of Baldur's Gate 3, and has several entrances.