Rogueport
The main town and starting point in Paper Mario: The Thousand Year Door. Mario comes here at the beginning of the game to meet Princess Peach because she found a treasure map. There is an item shop, the Lovely Howz of Badges, the Pianta Parlor and two entrances to the Rogueport Sewers.
The town is divided into five sections, the north side, the west side, the main plaza, the docks, and the east side. Mario will be moving through here constantly all throughout the game and you can find Luigi in all the areas in differnt chapters.
Rogueport in detail
North Side; The Excess Express, the Glitzville blimp, and sometimes Luigi.
West Side; Don Pianta's room, Peeka's Westside Goods store, the Pianta Parlor, Lucky with the Lottery Picks, and a grate to Rogueport Sewers.
The plaza; Zess T., Toad Bros. Bazaar shop, Charlieton, the Lovely Howz of Badges, the Podley's soda bar, and the gallow (noose platform).
The Docks; Lumpy, a Boat Mode platform, Cortez and the Black Skull (once you finish chapter 4), and Pa-Patch (before chapter 4).
East Side; Professor Frankly's house, Merlon's house, the pipe to Rogueport Sewers, Gus, the Robbo gang's hideout, the Trouble Center, Grifty, and Bobbery's house.