Buses 511, 512
Geographically speaking, Praia Vermelha might be secluded, but it also happens to be sandwiched right between one of the city's most famous landmarks, Pão de Açúcar, and its lesser-known neighbour Morro do Uribu, affording this slice of Atlantic Ocean a spectacular frame. Fortunately, with other things on their minds like the view from the top, that doesn't usually translate into sands crowded with tour parties, and even on the most glorious of weekends there is ample space between the kayak paddlers, fish-harpooning frogmen and sun-worshippers to settle into.
The angle of the beach also means that it opens out onto the ocean rather than the dirtier waters of Guanabara Bay around the corner, so only on days of adverse current is swimming not advisable, leaving those in the know to float on the calm waters and gaze up at the magnificent Sugarloaf above. The sand is coarse and golden, absorbing dawdling feet and making for a comfortable bed for anyone who overdoses at the churro (sweet donutty tubes) and pipoca (popcorn) stalls on the promenade. Just before sunset, take a 20-minute stroll to Bar Urca and perch on the wall, gazing out at the white sailing boats cutting across the bay, ice-cold beer in hand.