Castel Béranger is a block of flats in Auteuil, and its gate is what stops people on the pavement. The green cast iron is worked into curling shapes that everyone has called sea horses since the building went up, though nobody has established what they were meant to be. Hector Guimard finished the building in 1898 and designed every part of it himself: the brick and stone front, the gate, the door handles, the wallpapers, the carpets, the letterboxes. Neighbours called it the Deranged Castle.
Guimard kept building in Auteuil for another fifteen years, so the streets around hold half a dozen more of his houses within a few hundred metres. It is a walk of bay windows, iron balconies and front doors no two of which are alike. All of them are private flats. You look from the pavement, and the gates, the balconies and the front doors are the whole visit. The building won the city's first prize for a new facade in 1898, and the underground railway hired Guimard for its station entrances soon after.