What are the best day trips from Rio de Janeiro?

Petrópolis over everything else for a single day. It sits 65 km north of Centro at 845 meters elevation in the Serra do Mar, which means the air runs 8-10°C cooler than sea-level Rio. In June, expect 15-18°C up there. Buses leave Rodoviária Novo Rio every 30 minutes on the Unica Fácil line, R$35 each way (under $7), and the ride takes 1h20. The Museu Imperial, Pedro II's 1845 summer palace, still has its original jacarandá wood floors. They hand you felt slippers at the door. The history half of your pair burns 2 hours here happily. The foodie heads to Cervejaria Bohemia, where Brazil's oldest beer brand (founded 1853) runs a tasting tour for R$79 (about $15) that ends with 5 pours beside the original copper kettles. Meet for lunch at Casa d'Angelo on Rua do Imperador. The lasagna costs R$55, the dining room smells like wood-fired bread, and the portions could feed three. Last bus back leaves around 9pm, so dinner in Petrópolis is on the table too.

Niterói works when you want a half-day, not an expedition. The CCR Barcas ferry from Praça XV costs R$7.70 ($1.50) and crosses Guanabara Bay in 20 minutes. Sit on the upper deck. The salt wind is worth the spray. Oscar Niemeyer's Museu de Arte Contemporânea, completed in 1996, charges R$12 and perches on a clifftop at Boa Viagem. The view back toward Sugarloaf from the museum's curving ramp is better than the view from Sugarloaf itself. That's an opinion, but spend 10 minutes on that ramp and you'll likely agree. If one partner wants a beach while the other wants architecture, Itacoatiara is 25 minutes east by Uber (R$40). The surf there hits 2 meters in winter swells. Grab fried fish at Peixe Gato on Rua Gavião Peixoto before catching the return ferry. Not a full-day commitment. That's the point.

For a beach day that earns the commute, take Auto Viação 1001 from Novo Rio to Arraial do Cabo. R$85 one way (about $16.50), 2.5 hours. The water at Praia do Forno has 3-4 meters visibility in winter and runs 20-22°C in June. Cold enough that you notice. Boat tours to Ilha do Farol cost R$150 per person, last 4 hours, and pass through water so clear you can count stones on the bottom at 5 meters. The snorkeler in your pair gets the best cold-water diving on the coast between Rio and Vitória. The one who wants to sit still gets white sand and relative quiet on a weekday. Búzios is 30 km further east and carries the romantic reputation since Brigitte Bardot showed up in 1964. Honest take for couples, though. Búzios is better overnight. The Rua das Pedras bar strip doesn't pick up until after 8pm, and the last bus back to Rio leaves around 7pm. That's 5 hours of bus for 4 hours of beach. Save it for a weekend.

Paraty comes up in every recommendation list. It's 250 km southwest, 4 to 4.5 hours by bus on the Costa Verde line from Novo Rio, R$110 each way (about $21). The colonial center has thick whitewashed walls and rough granite streets that flood at high tide. Worth seeing. But 9 hours of bus for 5 hours of walking is a hard sell when you have limited days in Rio. Paraty wants 2 nights, minimum. For the couple where one person craves mountain air and the other craves a book and a terrace, try Teresópolis instead. It's 90 km north, R$40 by bus, 1h40 each way. The hiker gets Serra dos Órgãos National Park (R$44 entry, established 1939), where the Trilha Suspensa runs 3.5 km through Atlantic Forest at 1,100 meters. The non-hiker settles into the cafés on Rua Tenente Luiz Meirelles. Order the apfelstrudel. The Dedo de Deus peak, that finger-shaped granite spire at 1,692 meters, fills the window. You meet back in Rio for dinner by 8pm.