Paris
Better on the second visit, when you stop trying to see everything.
A city best seen from a bike, once you get out of the centre.
Amsterdam's problem is that the two square kilometres everyone visits are the least interesting part of it. The canal ring is genuinely beautiful and genuinely overrun; twenty minutes' cycling in any direction gets you to neighbourhoods where people actually live, with better food and no queues.
It's also one of the easiest cities in Europe to get around, provided you're on a bike. Rent one on day one and the whole city shrinks — distances that look like a tram journey turn out to be eight flat minutes.
Tulip season into early summer gives you long light and terrace weather, and September keeps it without the school-holiday crowds.
A workable shape rather than a schedule to obey — two fixed things a day, and room to change your mind.
Rent a bike on arrival — it's the whole point and the city is completely flat. Trams cover the rest, and an OV-chipkaart or contactless card works on everything. Never rent a car; the centre is hostile to them by design.
Amsterdam's constraint is timed tickets: the Anne Frank House and the Van Gogh Museum release on fixed schedules and go in minutes. Assign one person to the ticket run and keep the confirmed times on one shared plan, because a group of six trying to sync three separate bookings is how you lose a morning.