There are a few awesome viewpoints in Paris but I really love the Arc de Triomphe. You'll be close to it at some point in Paris, at least on a first time visit, when you stroll the Champs-Élysées. I love that the arch in my favorite park in New York, Washington Square, is based on this arch's design. It's also great exercise to climb the 284 steps (though you can take an elevator part of the way if you want - but suck it up and do it if you're able). We did it on our first day in town and it's a good way to stay awake while you're fighting jet lag.