LGBTQI+ scene
Wikipedia defines Lisbon's gay scene as "dynamic", with "several gay bars, pubs, nightclubs and beaches". The geographic core is explicitly identified: "most LGBT-oriented businesses are grouped around the bohemian Bairro Alto and the adjacent Príncipe Real and Chiado neighbourhoods".
The informal split: Bairro Alto = small bars, people in the street, a fluid LGBT/straight mix, cheap drinks. Príncipe Real = the iconic gay clubs (Trumps), a more select, late-night crowd. Cais do Sodré (Pink Street) = the start of the night, mixed. A compact scale: everything within 10-15 minutes on foot.