Ipanema

Ipanema runs between Arpoador and Leblon on Rio de Janeiro's southern shore, two and a half kilometres of golden sand with the Dois Irmãos peaks closing the western end.

The organising fact is social rather than physical. The beach is divided by numbered lifeguard posts — postos — and each has an established constituency: Posto 8 is the gay and drag beach with the rainbow flags, Posto 9 the artists and the left, Posto 10 the sports and family end, Arpoador at the eastern tip the surfers. Cariocas know which posto they belong to and the sorting is genuine rather than picturesque. When the sun sets behind Dois Irmãos the crowd at Arpoador applauds it, which is a real habit and not a tourist invention.

The song was written in 1962 at a bar two streets back, and the street the girl walked down is now named after the lyricist. That is the beach's export; the postos are what it actually is. The name is Tupi and means bad water, which referred to the fishing rather than to the swimming.

The water is open South Atlantic with a real shore break and rip currents, lifeguards along the length, and a flag system. Swimming needs attention. Water quality varies with rainfall — Rio's storm drains discharge along this coast — and the city publishes daily bathing assessments worth checking. Copacabana over the Arpoador rock is longer, older and more mixed; Leblon at the western end is the wealthier and quieter continuation of the same sand.

Find your posto. The beach sorts itself by who uses which stretch and the sorting is genuine — Posto 9 is not Posto 10 and everybody knows it. Read the flags, keep your bag where you can see it, and be at Arpoador when the sun goes behind Dois Irmãos, because the applause is real.