1: Auction
2: Shrine of Bane (formerly shrine of Ilmater)
3: The Pitt
4: Shrine (presumably of Ilmater)
When you first enter the plaza, you will be given the option of striding boldly forward, sneaking, or disguising yourselves as monsters. Striding boldly forward will get your ass attacked by groups of 10+ ogres and you will never even make it near the auction. Sneaking and disguising will both work, though I have found sneaking to be more effective. Disguising yourselves tends to get a lot of monsters checking you out. Sometimes you can bluff - being haughty works with the orcs and ogres, but with the goblins you have to be abusive. If you wander around for a bit you can hear some interesting tidbits of information. Not all are true, though.
Eventually you should make your way to the west side of the long building in the center for the auction. You won’t be able to win the item or stop what happens next, but presenting a report to the council is worth some kind of reward. Once the auction is over you won’t hear any more rumors, but you might still be stopped by monsters. Before you leave you might want to check out a couple of other places of interest in the Plaza area.
In the shrine of Bane is a robed orc who will invite you back in 2 hours - it is a trap. He will gather a bunch of monsters to attack you upon your return. Do not take the leather holy symbols - they are cursed and will cause the bearer to move at 3.
In the Pitt you may get into a fight with a drunk buccaneer. If you do, he has a longsword +1 and a suit of chainmail +1, but he might be tough to fight. If you spend some time mixing with the monsters, don’t drink heavily. You may wake up with all your money missing! It is possible you may fight another 4th level fighter in the bar - he has a magical longsword and suit of chainmail as well.
The shrine in the southwest corner can only be reached if you use a Knock spell to get past the magically barred doors. But once you are there, you can rest as long as you like.