Despite the name, Kal'atü'l-Üstad is not a castle but part of an instrument. İbrahim Hakkı built it as one element of a device for directing sunlight onto the tomb of his teacher, Fakirullah. Beside the tomb he raised a tower ten metres high; three kilometres away he laid a wall by hand without mortar, and opened in it a window of about a quarter of a square metre, which serves as the sight.
The alignment works twice a year. On 21 March and 23 September the sun lines up with the wall and the tower and with the head and foot of the grave: the light passes as though through that window, reaches the tower first, is turned there, and enters through the window of the tomb, resting for a few minutes at the head of Fakirullah. The provincial directorate quotes İbrahim Hakkı's reason for building it — that a sun which did not first light his teacher's resting place at the new year would be of no use to him.
The mechanism is delicate, and a restoration about fifty years ago put it out of true. Despite repeated attempts it stayed broken for decades, and only on 23 September 2011 did it begin working again.
When to go
- Climate
- Across Siirt as a whole, monthly mean temperatures run from 2.8 °C in January to 30.7 °C in July; the mean stays between 15 and 25 °C in May and October; rainfall is heaviest in March (112 mm) and lightest in August (2 mm). Long-term means for 1939-2025 from the Turkish State Meteorological Service (MGM).
