The Alaeddin Mosque, which is located on a hill in the middle of modern Konya, is one of the most problematical monuments of the Seljuk Anatolia. It has suffered from several restorations and almost lost of its original substance. Its irregular prayer hall shows the following parts (from east to west): a hypostyle hall, a central unit with a mihrap cupola and a western wing. An U-shaped courtyard, where two kumbets are situated, is positioned in the north side of the prayer hall. In addition, some wall fragments were recorded in the courtyard during a modest excavation in 1971. A further excavation in 1982 in the northwest corner of the hypostyle hall revealed the existence of another wall, which projects northward. There are several inscriptions in the complex, which give the names of the following Seljuk Sultans: Mesut I, Kılıç Arslan II, İzzeddin Keykavus I and Alaeddin Keykubad I. The irregular shape of the mosque and its building history have found some scholarly attention so far, but the site has never been the subject of a serious archaeological investigation. It has often been suggested that the central unit was the earliest part of the complex. The examination of Haluk Karamağaralı made it clear that the hypostyle hall was the oldest construction. According to Karamağaralı this was a single building with seven naves (south/north). He has correctly showed that the direction of the naves (north/south) was altered in a later period (east/west), probably during the addition of the other units. The arcaded wall, which separates today the hypostyle hall from the central unit, is interpreted by Karamağaralı as west wall of the first edifice. He believes that the arches were originally blind and they served as surface articulation. In his hypothetical reconstruction, the author divides the eastern wall into seven and the western wall into six vertically portions, while he separates each nave into seven bays. So that the supports, especially these of the western row, on his plan, are not positioned on the same axis with the piers, on which the arches rest. Some comments seem to be necessary. As noted also by Karamağaralı himself, the extreme northern arch, which is no longer visible, was later cut vertically and filled with mortared rubble, while both extreme southern arches were transformed into a triple arcade. There can be no doubt that this wall once possessed only five arches. Beyond that, the character of the arches indicates that they were originally complete open to a neighbouring construction, which was located at the western side. Such an organization is not unknown to the Seljuk architecture. Kölük Cami in Kayseri can be given as one of the examples. This construction, I believe, was (partly) demolished during the erection of the Tomb (kümbet) of Kılıç Arslan II. Karamağaralı assumes that the roof of the first mosque was originally supported by columns. But the size of the piers of the arcaded wall, which are clearly lower than the columns, makes it likely that they have originally corresponded with the similar sized (square or rectangular) freestanding piers, as in the Alaeddin Mosque in Niğde. A similar supporting system must have been employed also in the western unit. In his hypothetical plan, Karamağaralı adds a courtyard at the north side of the first mosque. He based his discussion on the projecting wall at the northeast corner of the hypostyle hall, but without considering the archaeological evidence from the excavation of 1971. The lack of a light opening in the roof of the hypostyle hall, according to Karamağaralı, is an additional proof of the existence of a former courtyard. As the original roofing of this hall is unknown, this idea finds no support. Based on the re-used Byzantine columns of the present complex, Scott Redford accepts the existence of a former Byzantine church in the site. Therefore he identifies the fragments in the courtyard, which he considered partly, as remains of this building. The re-used material may well be transported from somewhere else. The fragments in the courtyard indicate, rather, that the first Seljuk building has some integrated cells at the north side. Nevertheless the significant results can only be produced by a new investigation in the site. It is evident that the first building was a double construction, which included a medrese and a mosque. It seems that these two units were separated by an arcaded wall. The western unit oriented to Mecca, was probably the mosque of the complex, which was demolished during the erection of the Kümbet of Kılıç Arslan II. The eastern part may well be the medrese, which was mentioned in the written sources. In a later period, most likely during the era of İzzeddin / Alaeddin, the direction of the naves of the eastern part was altered, the piers were replaced by the columns and the central unit with a mihrap cupola and the western wing were added to the existed building. With other words, the building was finally turned into a kufa typus mosque, which still stands today. The irregular shape of this later mosque was most probably the result of the utilization of some remaining walls, the topography of the hill and the position of the kümbet of Kılıç Arslan II.