At the tourist office, you can buy a Pass Nantes, which allows you to enter museums and ride any of the city's public conveyances, including buses, trains, and some of the boats (summer only) that cruise along the river Erdre through the town. The pass costs 16€ ($23) for 1 day, 27€ ($39) for 2 days, and 32€ ($46) for 3 days.
The Secret Garden of Nantes
Two blocks east of the cathedral, you can visit one of France's most beautiful gardens, the Jardin des Plantes, boulevard Stalingrad, adjacent to Gare SNCF (tel. 02-40-41-65-09). The northern entrance is close to the Musée des Beaux-Arts, the southern border across from the train station. Admission is free. It is open March through October daily 8:30am to 8pm. In winter it is open only in November and December 8:30am to 5:30pm.