Achir or Ashir (Arabic: آشير) is a medieval city in Algeria, first capital of the Muslim dynasty of the Zirids, which ruled under Fatimid suzerainty in the 10th–11th centuries.

Thus, the Fatimid Caliph al-Qaim had authorized him to affirm his young power by the construction, in 935–36, of a capital that served as a stronghold and store on the slopes of Jebel Lakhdar at Ain Boucif.

At the beginning of the eleventh century, Al Bakri reports that 'it is ensured that in the whole region there is no place that is stronger, more difficult to take and more likely to discourage the enemy, because ten men are sufficient to defend it.

At the summit of Kef el-Akhdar, at an altitude of around 1,500 m, there were ruins that could only be reached by an impassable path leading from the dechra El-Hadj Ouel Ness, between the Oued el-Mezieb and the Chabet bou Djemel and Hadjar Sebah mountains.

Large boulders, joined together by low masonry, form the natural enclosure of the military establishment, the shape and details of which will be briefly sketched out, leaving it to the reader's own knowledge to interpret the true function of these ruins, which unfortunately have not been researched.

At one southern end of the bastion of the second enclosure, the masonry foundation ceases to be visible and is replaced on the rock by a chiselled recess 1.25 m wide and approximately 12 m long, the same width as the walls at their top.

At point K, which seems to have been used as a cistern to collect water and snow from the upper part (second enclosure), whose surface area is no less than 2,360 square metres, the wall then returns to the east-south side, at L and M, where, under a three-trunked oak tree, the Arabs made an excavation that they were unable to continue, but which was intended to allow them to enter under the enormous boulder I (which must have served as a lookout and still bears traces of sealing), it also seems to cover an underground passage or another cistern whose completely blocked entrance would be between the two walls still standing at the north-east corner of the building.

A perfectly regular wall would continue the line of defence as far as the small redan on which a stunted oak spreads its thin trunk, its branches gnawed by the goats of the neighbouring douars.

Excavations would be easy to carry out and would undoubtedly provide the key to the enigma that we have been trying to guess, as the ground leaves very little trace of these types of demolition, the small dimensions of which are easily erased and are very quickly covered by earth and later by scrub.