The Undercity

''Cantha is a nation of many, many people. The marketplaces are packed, the cities are overcrowded, and the sewers are overflowing with waste. Underneath the busy streets, the darker side of Cantha rears its ugly head. If you're looking to engage in unsavory activities, this would be the place to come.''

(This is an Explorable Area, not a City/Outpost)

You can find the Undercity via Wajjun Baazar: