Kissing the southeast corner of Plaza Vieja is this distinctive Gaudí-esque building, which remains Havana's finest example of art nouveau. Its outrageously ornate facade once housed a warehouse and a hat factory before it was rented by José Cueto in the 1920s as the Palacio Vienna hotel. Habaguanex, the commercial arm of the City Historian's Office, is in the process of a seemingly interminable restoration; the building, constructed in 1906, has lain empty and unused since the early 1990s.