Île de la Cité and Île St Louis
If you’re coming straight from the Marais consult your map and head down the rue des Nonnains d’Hyères. When you reach the Quai des Célestins cross the pont Marie which takes you to the île St Louis. If you’re starting afresh, make your way to Métro Pont-Marie (line 7) then cross the bridge to the island . This is one of two natural islands (the other is île de la Cité) on the Seine, characterised by narrow streets and elegant buildings. It doesn’t take long to circumnavigate the entire island on foot. Interspersed with the local boulangeries and fromageries are lots of touristy shops and cafés, some of which are worth the money and time, some of which aren't. I can highly recommend two good places to eat and/or drink: the St Regis and, on the opposite side of the street, the Brasserie ile St Louis (rue Jean du Bellay) . And if you’ve heard about the world-famous ice cream Berthillon, this is where you come to get it. Berthillon has its own tea room at 29 rue St Louis en l’île but is also sold at just about every café on the island.
Once you’ve finished here, consult your map and take the connecting bridge to the île de la Cité which is situated at the intersection of rue Jean du Bellay and the quai d’Orléans. As soon as you are on the other side you will be right by the Cathedral of Notre-Dame. As you’ve come all this way it would be rude not to go in but please remember that it functions as a place of worship as well as a tourist attraction. Outside of the main entrance is the Parvis Notre-Dame (which is an open space), situated on the far side of the Parvis is the Archaeological Crypt which displays ancient remains found under the Cathedral during renovation. It won’t take long to get around and makes a rather wonderful addition to your sightseeing (imho).
Also on this island is the Sainte-Chapelle (4 boulevard du Palais, 75001) which is a must-see. A royal medieval Gothic chapel which was consecreated in 1248, it was commissioned by King Louis IX (Saint Louis) and is one of the earliest surviving buildings of the Capetian royal palace. And your final stop for the day is the Place Dauphine . At the western tip the island, it is a beautiful place to sit and watch the world go by, either from a bench or from the terrace of a bistrot. Either way, it’s time to stop, have a refreshment and think about dinner. You might be tempted to try one the restaurants which mostly have so-so reviews on Tripadvisor. However, I can happily say that the food and staff at the Rose de France are worth a visit.