Alfama Springs, Lisbon, Portugal: Cultural Geoheritage Throughout the Centuries

The existence of several springs located in the Alfama district, Lisbon, Portugal, reported since the medieval Islamic period, is an important but almost unknown part of the history of the city. The word “Alfama” probably comes from the Arabic “Al-Hamma,” which means “hot spring.” This historical importance is revealed through the diversified water usage, such as ship water supply during the Portuguese marine expansion period from the fifteenth century on, or even the way of living of the zone, materialized not only by the existence of laundrywomen in the area but also with several commercial and daily activities related with the water. Some of these springs had temperatures above 20 °C and significant therapeutic properties, which made them object of an intensive search and usage by local population and surrounding areas. Water from these springs, meanwhile totally sealed and abandoned more than 40 years ago, was qualified as “mineral water” by the authorities and was therefore used in several public baths, known as “Alcacarias,” by the end of the nineteenth century. These “Alcacarias” were used by the Lisbon population for decades and were also very influent in the city living. The appearance of the “Fonte das Ratas” spring, in the 1960s, has also contributed to keep the memory of the Alfama springs alive up to today, mostly to local inhabitants. Recently, research work comprising geological, hydrochemical, and geophysical works was conducted in the area to achieve a better understanding of the hydrogeological conceptual model of the Alfama thermal springs (distribution and characteristics, flowpaths, mixing processes, etc.) and their relation with the local tectonic framework. This paper shows, in a simplified way, the geographical spring location based on historical documents and archeological data, as well as the geological and hydrogeological characteristics that constrain the area. The paper also shows the way these waters were exploited for several centuries, leading to the concept that the real heritage of the Alfama district lies underground, in groundwater that can no longer be seen by the population or its visitors. Some considerations are also made on possible future uses of these waters, once the characteristics that made them famous are confirmed nowadays.