You can't come to Paris without seeing the Eiffel Tower.
I purchased a ticket in advance with second level access, which worked out with me.
I'm afraid of heights and I wasn't that eager to go to the very tippy top!
It was cold, damp, and drizzling when I got to the second level but it was still an incredible sight.
The place was packed, no surprise, but the crowds won't lessen the enjoyment you'll get from knowing you finally made it to this most iconic of landmarks.