Leilani was the capital of Alderaan's sister planet Delaya. The city was packed with faceless duracrete factories that produced large amounts of smog. It had narrow streets and many unfinished construction buildings that littered the landscape.
Shortly after the destruction of Alderaan in 0 ABY, the city was full of Alderaanian refugees too poor to leave the planet. Princess Leia Organa visited the planet to monitor the refugee problem, as well as recruit new soldiers for the Rebel Alliance.