Our first niece was just a babe in arms at our wedding twelve and a half years ago and a toddler when we lived near Chicago years ago, when I was in my early twenties and just getting used to big city living. Now she's on the cusp of becoming a teenager.
She lives in Illinois, so I gave her a few options - Chicago, Milwaukee, the Wisconsin Dells. She chose Chicago. All those years that she's been growing up, I've been navigating cities, so it was fun to show her the ropes. Since she was game for whatever, we spent our time the way I typically travel: taking the train, walking way too much, packing it in, shopping just a little, eating on the run, visiting a museum, buying tickets for a play that same day after researching every play in the city weeks before. She didn't get tired one bit. I very much needed a nap before it was dinnertime, but she easily could have kept going all night.
I love that she's in the in-between. She knows it too. Growing up is something she has to do. She kind of wants to and kind of doesn't. My best advice for navigating being a teenager was to stick with your closest small group of friends. With good luck, they could be your friends for a long time, and they'll help you get through all the stuff that isn't so great. And I told her to wear what you want to wear. And as far as make-up goes, I only wear eyeliner on special occasions.