Rio Grande is the old maritime end of southern Brazil, a port city where Lagoa dos Patos drains toward the Atlantic. It was the first capital of Rio Grande do Sul, and the centre still has churches, customs houses, and civic buildings from a time when shipping gave the city its weight.
The appeal is not polished resort Brazil. Rio Grande is windier, flatter, and more working than that, with docks, university museums, fishing boats, and the long road out to Cassino Beach. That mix makes it more interesting than it first looks, especially if you like places where geography explains the city.
Give Rio Grande a spare day if you are already travelling the far south. Start with the Oceanographic Museum, walk the old centre around the Cathedral of St Peter, and leave time for the open Atlantic scale of Cassino Beach and the stone jetties at the harbour mouth.