Île Saint-Louis, River island in the 4th arrondissement, Paris, France

The Île Saint-Louis is a parallelogram-shaped island in the Seine, 525 m long and 250 m wide, upstream of the Île de la Cité and linked to it by the Pont Saint-Louis. Four quays ring it, and the rue Saint-Louis-en-l'Île runs its length parallel to the river. Its stone embankment walls carry a parapet and a row of trees, behind which stand five- to six-storey pale-stone houses with grey mansard roofs; at the eastern end rises the Gothic church of Saint-Louis-en-l'Île with two square towers, a rose window and a tall flèche.

Two islands, Île Notre-Dame and Île aux Vaches, were separated by a Seine arm until 1614, when Louis XIII entrusted Christophe Marie with their development. Marie filled the channel, built stone quays against floods and laid out straight streets; the Pont Marie was finished in 1635. Building began around 1618, and from 1638 nobles added private mansions. The island took its present name in 1726, after Louis IX.

Residents are called Ludovisiens or Ludoviciens. The name dates from 1726, when the island was dedicated to King Louis IX, canonised in 1297; during the Revolution it was briefly renamed Île de la Fraternité. At 17 Quai d'Anjou, the Hôtel de Lauzun housed Théophile Gautier and Charles Baudelaire, who met there in the Club des hachichins.

Five bridges serve the island: Pont Saint-Louis from the Île de la Cité, Pont de la Tournelle and Pont Sully from the left bank, Pont Louis-Philippe and Pont Marie from the right bank. No metro line runs onto the island; the nearest stations are Pont Marie and Sully-Morland on line 7. Rue Saint-Louis-en-l'Île is the only street running parallel to the Seine, all others cross it at right angles.

The main street, Rue Saint-Louis-en-l'Île, is home to the famous Berthillon ice cream shop that has drawn visitors for decades. Alongside it stand well-preserved townhouses from the 17th century that show how affluent families once lived.