A mellow riverside town, Gualeguaychú is quiet out of season but kicks off in summer, with the country’s longest and flashiest Carnaval celebration. Make a stop here any weekend from mid-January to late February and you’ll find things in full swing. The main venue is the Corsódromo, where admission is AR$120 to AR$150 most nights.
There’s a string of decent budget hotels along Bolívar between Bartolomé Mitre and Monseñor Chalup, and three hostels in town.
Gualeguaychú is easily reached by bus from Buenos Aires (3½ hours), Paraná and other towns along the Río Uruguay. Gualeguaychú is also a crossing point to Uruguay: the town of Fray Bentos lies just across the bridge.