My three favourite black holes are:
The one in the center of our galaxy : It is the closest supermassive black hole we know of and is found in a region called SagitariusA*. It’s what all the stars in our galaxy go around, and offers us a good chance to find out about extreme gravity!
NGC 1277: It’s found in the Perseus cluster. It’s one of the biggest known blackholes in the universe with upper estimates of 30 Billion times our sun! It’s another galactic center, but this one has lost a lot of it stars. It’s interesting to find out the history of this black hole.
Cygnus X-1: This is a smaller black hole, but it was the first known! We found it because it’s slowly eating another star. This is making it produce some very bright x-rays. You can tell by the name where this one is found 🙂 It’s in the Cygnus constellation! This black hole has taught us a lot about gravity and continues to do so.