the water stairway, located in the generalife, has been to said to have maybe been designed to help with ablutions (washing) before prayer, which is required by muslims. the water that runs down this channel comes from the sultan's own private conduit.
the whole effect of the water stairway, and the fountains throughout the alhambra, are one of peace and calm. never have i felt such a calm, even when crowded by loud sweaty tourists! the trickle of the water, the serenity it provides, is beautiful. the poet juan ramon jimenez said it best i think,
i heard the music of the water more and more
yet at the same time less:
less was my blood, my life
and i heard that the music of my life and
blood was the running water.


