All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
As-haabul-Hijr who are mentioned in the Saying of Allah (which means): {And certainly did the companions of Thamud deny the messengers.} [Quran 15:80], are Thamud the people of Saalih ; Allah has mentioned their story in more than one place in the Quran.
At-Tahreer wat-Tanweer (14:72) reads: “The people of Saalih are Thamud; they used to encamp in Al-Hijr, which is a place prohibited for some people due to some of its characteristics, or that it is derived from al-Hijaarah (stones) because they used to carve from the rocks of mountains, houses, feeling secure. These houses were built in floors and there is a great well in the center of these houses, and many other wells [around].
Al-Hijr is the one known in the valley of the villages, and it is between Madeenah and the Levant. It is known today by the name Madaa-in Salih, on the way from Khaybar to Tabuk.
Allah knows best.