Sundial

Gnomonics, the discipline that studies the form in which sundials are constructed, was developed by Muslim astronomers. One example is the sundial in the Museum of the Alhambra. This is a solar quadrant, a type of sundial in which night and day have hours of the same duration within the same day, but of varying duration according to the season of the year. 
This sundial marks the time through a series of grooves and the solstices of winter and summer with two semicircles. It also has some signs of the zodiac and inscriptions in Kufic characters which in a similar way to a map legend mark the times of daily prayers.  The hole in the centre was for the gnomon or metal rod that cast the shadow indicating the time of day. 
Of all the different marks that can be observed, there is one of particular interest inside the semi-circle in the south-eastern part of the sundial. It has been variously identified as a pair of tongs or of compasses and on other occasions as a mihrab pointing in the direction of the wall of the Qibla (the direction that Muslims should face when praying).  In spite of having all these interesting features this sundial is not a decorative object and in fact is totally functional.
This piece had two functions. Firstly, to indicate the time of day and secondly, its religious application to mark the various prayer times. 
The fact that this type of sundial had to be positioned in a very precise, exact location casts some light on its specific original use.