They had a practical as well as decorative purpose, protecting buildings against fires, after much of the city was devastated by fires during the Great earthquake in the 18th century. We visited the wonderful Museu Nacional do Azulejo set in the church and cloisters of Madre de Deus but soon realised that the whole of Lisbon is like a living tile museum!
Attractive tiling adorns shops,private houses and cafes, such as the Leiteria Anunciada in Rua de Sao Jose, a former dairy, shown below.
A recently published specialist guide book documents some of these attractive buildings and shops. It's called Old Charm Lisbon, Retro and Vintage Establishments by Ana Da Silva.
As a stamp collector I was pleased to discover that there are quite a lot of Portuguese stamps depicting tiles including these in the Castel Sao Jorge.
Tiles on Stamps - cheaper than the real thing, and they don't need all that grouting!