If you pull up the map while you are in AstroCity you will see it (unmarked) on the
southwest corner of the map, it has a narrow path and widens out.

You can put up the map, then click on the worls and click astro city in the exact corner
of the southwest there is a U shape, the black hole is in the middle of the "U". :)

Sorry above in my earlier answer i meant "world" not "worls" :) sorry!

U HAVE TO JUMP THROUGH THOSE HOLES IN THE GROUND I FOUND IT...BUT COULDNT GET IN I HAVE
NOT GOTTEN THAT FAR...BUT I CAN TELL U.. ITS LIKE THE SPEED WEEDS IN FRIGHT FEAST.... AND
MAKE SURE U TAKE UR TIME AND GO EVERY WHERE I HOPE THAT HELPS

If you pull up the map, it will show you in a little picture is a tiny passage way and it
kind of looks like a different part but it's not its still connected and if you go there
{located on the bottom left corner} you will see grumps and the black hole... i really
hope that this really helped a little bit:)

If u look at the astro city map, in the bottom left hand coner u will see a letter C
looking thing. Go under that, find the bridge and u will find it

well i have no clue at all . i look alll the time

Go to solar shot in astrocity. Look around that. There is a long walkto the left of the
game. Follow that path, and it will lead you to the mini black hole.

Dirty brown road to the left. Its not a sidewalk. Keep going until you are at the end.
There you will see black hole and the evil wizard who has an evil package for you to
deliver to frankenhisname the scientist another mission. Blackhole is in very bottom left
corner of astro city. Good luck

How to dispose the gooey stuff, give a prize toy to that blackhole thingy, then you're
done, then talk to evil guy, another mission. Secret:
Found the way to that amusement park that was banned. Solve the ghost in the maze craze
alexander find him he will give you an entrance to the banned amusement that was closed.
But before that alex the ghost wants a pet toad friend, you need 50 coins to buy a frog at
the pet store, then bring frog to frankenhisname the scientist in freightfest to change
the frog to a toad. Bring the toad to alex in the maze craze and you got your entrance to
the amusement park, its broken, you need to fix it! Good luck! To beat the maze craze to
find alex go to search on the side of your computer and ask "how to find alex in six flags
nintendo wii", then look for www.cheatmaster.com . Good luck!!