You have to go and see this basilica, even if you're not religiously inclined. It was built at the end of the 19th century at the top of the Montmartre hill in Paris. Its famous "white pastry-like" architecture dominates the city.
The Sacre Coeur district offers many spectacular views on Paris: its village-like streets and squares, its cafés and restaurants. But, as you walk a few meters away from the core tourist area, you discover very quiet and charming spots, quite unexpected in such a large city as Paris.
You can easily get there by Metro, but be prepared for a short walk up the hill!