The Old Galactic Market is were i spent level 10 and 11 as a smuggler, should be the same for all republic classes (assuming you did most of the side quest on your origin planet). Your asked by a senator to go to the old Galactic market and help clean it up. After the sith attacks, a bunch of aliens moved in to the market, and gang called the guild started to ask for protection money and now runs the show.
The first part of the market is under Republic control. It kind of the area were you pick up quest, there is also a large cantina to hang out in (or to log out in to get the rest XP). Once you have picked up for 3 or 4 quest in the area it time to move over to the other side of the market (which is in another building).
So very early on in the Old Galactic market (when you get to the side you can kill thing), is that you’ll see the zone Champion. I don’t know if every zone has a champion, i heard rumors that they do, but this is only one i’ve seen, it also isn’t hidden almost everyone will walk past it at some point. I also couldn’t tell if the name was SD-O (the letter O) or SD-0 (the number zero), i’m assuming it is zero since most droids end with a number.
The second building is pretty much the old Skyline Mall, which is now were the guild lives. It does have a mallish feel to it, and you do feel like you in one of the more poorer area of Coruscant. One of the complaint i have is almost all areas of the planet, look very similar, yes there are some great shot of each, but the not so great area just kind of feel the same.
Spoiler…. Stop reading if you don’t want the story ruined (this is for all classes)
Once you’ve completed all the quest here you’ll find out the senator that sent you down here to kick the rebels out, took money from the rebels and had promised to help them. You’ll have to make a light side dark side choice in that quest.