Paris at night
Paris changes character after dark. The pale stone of the buildings throws back the streetlight, the river turns into a mirror, and monuments that compete with traffic by day stand alone in the dark. It is by far the best time of day to see it.
The sparkle, on the hour
From nightfall until one in the morning, the Eiffel Tower sparkles for five minutes at the top of every hour with thousands of white lights. It costs nothing to watch: you just have to be nearby. The classic spots are the Trocadéro esplanade and the Champ de Mars, but from the water you see the whole tower with nobody in front of you.
The river, where the show is
At night the Seine does something it cannot by day: it doubles the city. The lit bridges, the Orsay facade, Notre-Dame and the Conciergerie appear twice, above and reflected. An evening cruise covers all of it in an hour, and since the ticket has no assigned time you can decide on the spot which sailing to take.
The Arc, open late
Few people realise the Arc de Triomphe stays open until 22:30, so you can go up well into the night. From the terrace the twelve avenues become rivers of light, with the Eiffel Tower sparkling in the distance. Bear in mind that last admission is 45 minutes before closing.
A walk that works
From the Pont Alexandre III to the Pont Neuf along the left bank is a little over half an hour on foot, almost all of it by the water with the embankments lit. It is the city's most rewarding night walk and it costs nothing.