Luanda in 3 days: the Angolan capital where 5.7 million enslaved people departed for the Americas over 300 years, where Gustave Eiffel's prefabricated iron palace ended up by mistake, where the world's largest informal market has 250,000 traders and no official count, and where the slow, sensual dance music that swept European salsa clubs was born in a post-civil-war Luanda neighbourhood.