A red carnation against a dark coat is about the simplest strong frame a street photographer can ask for, and on 25 April Lisbon is full of them. Freedom Day marks the largely peaceful revolution that ended the dictatorship, when civilians pushed carnations into soldiers' rifles, and the flowers are still sold on street corners and pinned to jackets. The rest of April is good working weather, with highs about 20°C and around 11 hours of sun a day.
The picture to plan for is the afternoon march from Marquês de Pombal down Avenida da Liberdade to Rossio. Skip the wide crowd shot. Work from the edge with a short telephoto and isolate single flowers against coats and banners. Later on the sun drops over the avenue's western side, and from the east pavement it comes through the petals from behind.
Start the night before. Most years a crowd gathers at midnight in Largo do Carmo, the small square where the old regime surrendered, to sing "Grândola, Vila Morena", the song whose radio broadcast told the troops to move. Bring a fast lens and leave the flash in the bag.
On any other morning, be at Miradouro da Senhora do Monte, above Graça, for sunrise. The castle and the Baixa lie below you to the south, with the 25 de Abril Bridge, renamed for the revolution, off to the right. The early light comes low from your left and rakes across the rooftops, and you will have far more room than at sunset.
Expect rain on about ten days. Keep a cover for the camera and go out the moment it stops. Rossio is paved in black and white stone laid in waves, and when wet the whole square becomes a mirror, holding the streetlamps for all of blue hour, which in late April falls not long before nine.