Tiana's Palace is a restaurant owned by Tiana. It is located in an old sugar mill, a building which had been empty for over twenty years and was under the ownership of Fenner and Fenner Real Estate. Tiana's father was the first one to dream about opening a restaurant here, where he would serve his home-made gumbo together with his daughter Tiana. He couldn't save up for the place, though, because he had to work three jobs to make sure his family had enough money.
After Tiana's father passed away, Tiana started saving up to get the restaurant as well. She worked extremely hard and much to make sure she had enough money to pay for her and her mother's expenses, as well as save for the restaurant. She mostly saved up tips from her waitressing jobs. Once Charlotte La Bouff paid a large amount of money to her for a lot of man-catching advice, Tiana finally had enough and placed a bid on the old sugar mill. Fenner and Fenner then promised to bring her the papers to sign.
However, the Fenner Brothers later told her she was "outbid", however, but as unlikely as it is that someone would bid on the mill after twenty years of it being untouched in the same week Tiana placed her bid, the Brothers probably made that up to prevent having to sell the mill to a woman of colour. Once Tiana returned to the Fenners' with her alligator friend, however, she was able to pay for the building and open her restaurant.
With a lot of effort on her and her husband Prince Naveen's behalf, the building was transformed into a restaurant, not named like Tiana's father had imagined it, Tiana’s Place, but Tiana's Palace to emphasize her new title. Also, Tiana, while married, was still very much in charge of the entire business. The restaurant became the crown jewel of New Orleans, even inspiring the other buildings in the neighborhood to become vibrant and reinhabited. It became revered as the favorite restaurant of visiting royalty - Naveen's parents, the King and Queen of Maldonia - and also hosted a live jazz orchestra, the Firefly Five plus Lou, led by Louis.
Presumably Tiana and Naveen live in the restaurant, which would make it one of the few locations inhabited by a Disney Princess at the end of her movie which is NOT a palace (despite the fact the restaurant is called a palace). Others who don't live in a palace are Pocahontas, who remained in her village and Mulan, who presumably moved into a regular home or stayed at her parents' cottage.
There is a direct pun in the name of the band. The name "The Firefly five plus Lou" is a pun on the name of the band Firehouse Five Plus Two, which was a Dixieland jazz band, popular in the 1950s, consisting of members of the Walt Disney Studios animation department.
The theme design for Tiana's restaurant seems to be inspired from Lily of the Valley and Lotus.