Port Louis is the capital and commercial heart of Mauritius, founded by French governor Mahé de Labourdonnais in 1735. It sits in a natural harbour sheltered by a ring of mountains, and despite heavy development it still has corners of genuine colonial atmosphere.
The central market is the best place to start. It's a covered market selling fruit, vegetables, spices, street food, and an enormous amount of textiles — loud, colourful, and completely real. Nearby, Chinatown has been there for 150 years and still feels like it. The Aapravasi Ghat, a UNESCO World Heritage Site near the waterfront, is the landing point where hundreds of thousands of Indian indentured labourers arrived from 1834 onwards. The small museum there is sobering and well done.
The Caudan Waterfront — a redeveloped harbour precinct with shops, restaurants, and a casino — is popular with locals and tourists alike. Prices here are noticeably higher than elsewhere in the city. The racecourse at Champ de Mars is one of the oldest in the southern hemisphere and draws big crowds on racing Saturdays (July to November).
The Natural History Museum on the main square, Place d'Armes, has the best collection of dodo remains in the world. It's free and worth 30 minutes. The city centre is compact and walkable, though traffic is severe during rush hours.