Levadas are irrigation channels or aqueduct specific to the island of Madeira, that originated out of the necessity of bringing large amounts of water from the west and northwest of the island to the drier southeast, which is more conducive to habitation and agriculture, such as sugar cane production. In the past they were also used by women to wash clothes in areas where running water to homes was not available. The idea of this style of water channel was brought to Portugal by the Moors during the time of al-Andalus (or Muslim Iberia).
To be honest I had no idea to this moment what exactly these images show lol, I just thought they are beautiful and reflect my wish to come back to the island for some nature trekking. Moreover, I matched a Madeira nature stamp only to learn it is also of a levada, the 25 Fontes.