Versailles & flexible Paris

The plan

Morning — Palace of Versailles. RER C train from central Paris (~40 min). Book Passport tickets in advance — they cover palace + gardens + Trianon estates. Plan on 4–5 hours.
Afternoon & evening — back in Paris, split up however you like. Options:
- Le Marais — historic district with 17th-century mansions, Place des Vosges (the city's oldest planned square), the Jewish quarter on Rue des Rosiers, falafel, vintage shops.
- Sainte-Chapelle — small royal palace chapel from 1248 wrapped in 15 floor-to-ceiling stained-glass windows. One of the great Gothic interiors in Europe.
- Sacré-Cœur — the white basilica on top of Montmartre, with a sweeping view of the city. The funicular skips the steep climb.
- Montmartre wandering — the artists' quarter around Sacré-Cœur: narrow lanes, Place du Tertre with portrait artists, the old Au Lapin Agile cabaret.
- Berthillon — the cult family-run ice cream parlor on Île Saint-Louis (the small island in the Seine). Closed Mondays and Tuesdays.
- Latin Quarter — the lively Left Bank district around the Sorbonne. Cafés, bookshops, small restaurants — good area for an unhurried dinner.

Versailles is best in the morning before the crowds. The gardens close later than the palace — save them for the back half of the visit.