(Urban) cycling trip destination suggestions

[p nut]

Summer is over halfway done for my kids and I feel the need to spend more time with them. The oldest is 15 and she’s a runner. And likes to bike as well.
I am thinking of taking her and flying to a city and sightseeing using our bikes. Fortunately, I have 2 Bromptons that we can take.

She’s not an avid cyclist so somewhere flat-ish where we can bike around easily. And Points of Interest not too far from the city (we’ll be in a hotel). Of course, needless to mention, good, safe bike lanes or paths.

Due to the time of the year, I guess this limits me to the northern part of the U.S. or maybe even Canada. But please feel free to post all possible places, as there is a mini-break in October we can use as well.

Hopefully, big enough city with a major airport so we can get there cheap(er) and quick for a weekend trip.

Any suggestions?

Couple places I was thinking, that I haven’t spent any time in are Minneapolis and Portland (OR).