Up to 16,000 migrants were held at one facility.
I asked the detainees to send me their "location" using encrypted apps. That's how we were able to learn that migrants are not held at formal prisons, but at locations publicly referred to as "immigration centers" that actually have massive built in prisons.
I'd have to dig up the coordinates on my old phone, as it has been four years. But one of the torture holes is near the Holy city of Mecca.