‘Salsabil‘ is an Arabic term referring to a spring or fountain present in the Yanna, the paradise promised by the Qur’an to Muslim believers. The fountain also appears in some hadiths – that is, in Islamic oral traditions associated with the lineages of people who are said to have heard them from the Prophet Muhammad and repeated them. However, it is mentioned only once in the holy book, in Sura 76 (Al-Insan), verses 17-18, to say “a fountain therein which is named Salsabil”.
This verse could refer to an earlier verse naming the drink (Zanjabiil, or ginger) provided to those who enter the Yanna. Again, in this context, Salsabil is usually, but not always, regarded as a proper name rather than a common name. In any case, this term is probably the origin of another term used to designate a type of fountain, in this case as a common name. It is this one that we are going to deal with, and not so much for linguistic reasons, but because of the very special structure to which it refers.
A Salsabil is in fact a fountain that basically consists of an inclined plane – sometimes also a channel – with varying reliefs and mounted on a wall, through which a subtle sheet of water is allowed to flow. Its particular function is to maximise the surface area in contact with the atmosphere and, therefore, the evaporation of water. This allows the aeration of the liquid element, in the case of drinking water, or the evaporative cooling of buildings and rooms. However, we should not underestimate the value it had – and has – as an ornament, for some Salsabil are beautiful works of engineering and craftsmanship in stone or marble.
And yet, it would seem that the Salsabil may have had another function. As quoted by Filiz Ozer of Istanbul Technical University in Splendors of Topkapi, Palace of the Ottoman Sultans journalist Stanley Maisler, “in an Ottoman room (…), if you see running water, you know the room was a meeting place. Water conceals voices”. Be that as it may, the use of Salsabil extends from southern Spain to northern India, while still reaching North Africa and the Middle East.
Sources: Wikipedia 1, Wikipedia 2, Cambridge Org, Stanley Meisler, Quranic Arabic Corpus.