During the expedition “Ernst von Sieglin” to Alexandria in 1900/01, an excavation was carried out at the eastern harbor of Alexandria, in the so called Basileia. Although the publication was prepared and announced in the following years, it was never realized. Recently parts of the documentation, the day book, drawings, and photographs of this excavation reappeared and based on this material and yet unpublished finds that are housed in Tübingen, the talk will discuss a possible interpretation. Considering the excavation methods of around 1900 and the fragmentary documentation, a secure reconstruction is not possible. The photographs and drawings though allow at least a reconstruction of a cistern of Late Imperial times that was connected to a luxuriously equipped building – either baths – or more likely a residence. Therefore, the talk will include a part from questions regarding the water management in Roman Alexandria, the comparison with other similar complexes in North Africa, and, based on the architectural fragments, parallels with Asia Minor.