The great rectangular lawn running south-east from the foot of the Eiffel Tower to the École Militaire, the Champ de Mars began as a military parade ground and is now the city's most famous picnic spot. The full sweep of the tower rises at its north-western end, and the grass fills on any fine day and evening with locals, students, and visitors uncorking wine and waiting for the tower to begin its hourly sparkle after dark.
It is free, open, and one of the simplest pleasures in Paris. Avoid the worst of the crowds and the hawkers by coming early in the day, or commit to the evening and bring a blanket — the light show on the tower, every hour on the hour after sunset, is best seen flat on your back from the lawn.