Carnations are simple flowers to most of us, but in Portugal they were important in what's called the Carnation Revoultion, or "Revolução dos cravos". On Apr 25, 1974 a group of people had enough of the dictatorship that had started in 1926 and took matters into their own hands. They started a non-violent revolution in which no more than 5 people died and Portugal became a democracy. Soldiers used a red carnation in their uniform shirt pocket to identify those in favor of the revolution.
Now, every April 25, also known as dia da liberdade (or freedom day), you'll most likely see red carnations around the towns.
Portugal has a long tradition of making azulejos and using them, not only inside the houses and apartments but also on the outside and on street signs.
The pictures on this tip portray tiles found walking towards the town center and at Igreja de Sao Joao Baptista (picture #3).