Looking for things to do during a weeklong stay

Hi y’all, I’ll be in Miami from the 17-24 this month. I’m freshly 18 and this is my first “solo” trip as an adult.

I’m really here to visit my brother (I’ll be bunking with him in Brickell) but he’ll be working and won’t have much time to take me around. This is my 5th trip to Miami and yet I haven’t seen most of the touristy famous places Miami has to offer.

I’d love any suggestions you guys have, please note that I probably won’t have a car coming from Brickell. Thanks!