The Sir Seewoosagur Ramgoolam Botanical Garden at Pamplemousses is one of the classic excursions from Port Louis. Laid out in its present form by Pierre Poivre in the 18th century, it still carries the atmosphere of the spice-trade era: avenues of palms, old colonial planting schemes, and ponds filled with giant Victoria water lilies.
The garden is easy to underestimate if you rush it. Give yourself time to wander, look for the talipot palms that flower only once before dying, and hire a guide at the entrance if you want the plant stories rather than just shade and paths.