"This is a map of the underground market," Zeke said, flattening the map.
The area of the underground didn't seem that big. It was just because of the fog that made it look big. But thanks to the map, they're able to imagine the land area of the underground market.
The location Angelo said to be the dangerous part of the underground market was the pub. Yes, the pub isn't any regular drinking store. Rather a place to get information.
However, getting information inside the pub was a huge risk as they have one weird rule. If you want information, you need to fight for it. Challenge the person you want to get information from, and if you win, you will get the reward you want.
The people who hold information in the underground market are called the revealers. Zeke wasn't a revealer, but he knew something that they didn't, as he was a former member of the organization.