When I was staying in the Albaicín district of Granada every night there was a strange metalic piping noise every few minutes. It sounded like a very loud mobile phone or some sort of alarm.

Maybe some sort of synthesized clock chime.

I would love to know what it was.

What you were hearing was the Scops owl.
The males fly around the Albaicín at night and unless you know what it is you can easilly think that it is a man made sound.

There is a sound file and more info here.
https://en.wikipedia.org/wiki/Scops-owl

The Albayzin is not really a place for ornithology but in April and May it is common to  hear nightingales singing under the Alhambra on the Darro river. Hearing this in moonlight is especially pleasant.