Next to the Hellenistic Heroon, stands another burial monument of Ephesus, known as the Octagon. Dating back to the late 1st century BCE, this building was a monumental eight-sided mausoleum, around 13 meters high, originally surrounded by a Corinthian colonnade, standing on a square base with the sides 9 meters long. It was covered, most possibly, with a steep pyramidal roof, a novel architectural solution. All visible parts were made of white marble.
Today, not much can be seen of the original octagonal building. Only its square pedestal is still standing on the Curetes Street while many fragments are in the storage of the excavation site. However, two columns and some pieces of the cornice were removed to Austria in the early 20th century and are now on display in the Ephesus Museum in Vienna.
The Octagon was discovered in 1904, and it was first interpreted as a trophy-monument. However, further excavations carried out in 1929, found a burial chamber situated on the top of the basal structure. Inside, there was a sarcophagus with the skeleton of a young woman of 15-18 years at the time of her death. Unfortunately, the skull of the skeleton was later lost in Germany during the Second World War. In classical antiquity, intramural burials were reserved for the most prominent persons, such as heroes, wealthy sponsors of public buildings, or influential politicians. Thus, the archaeologists were more than surprised to discover the mausoleum apparently erected to honour a very young woman. As no inscription was found to explain who it had been, the riddle is still unsolved. However, a sensational suggestion was made in the 80-ties of the 20th century. Hilke Thür of the Austrian Academy of Sciences suggested that it was the tomb of Arsinoë, an Egyptian princess murdered in 41 BCE by Mark Antony, at the instigation of Cleopatra VII. The dating of the tomb seemed to confirm this theory as it was dated to the period between 50 and 20 BCE. Moreover, the octagonal plan of the monument that resembles the second tier of the Lighthouse of Alexandria and the pyramidal shape of the mausoleum's roof seemed to point out in the direction of Egypt. However, the carbon-dating of the bones conducted in that period gave an extensive range of dates, between 200 and 20 BCE.
The author of "the tomb of Arsinoë" theory, Hilke Thür, made many attempts to prove her point. DNA tests failed, because the bones had been handled too many times. Thus, a reconstruction of the missing skull was made, based on the old photographs and measurements made in the 1920s. The computer reconstruction supposedly demonstrated a mixture of African, Egyptian, and classical Grecian features — precisely as it should be expected of Arsinoë's appearance. However, the method of reconstructing the ancestry on the basis of skull measurements has long been discarded as a pseudoscience.
The best summary of the "the tomb of Arsinoë" theory was provided by a renown classicist, Mary Beard, who pointed out the reasons why this interpretation does not add up. First of all, there is no preserved inscription with the Egyptian princess' name on the tomb. Secondly, the remaining bones (minus the missing skull) are said to be of a 15-18-year-old while Arsinoë may well have been in her mid-20s when she was killed. Thirdly, the assumption that Cleopatra and Arsinoë were full sisters is not confirmed as the only thing known is that their father was King Ptolemy, while they may have had different mothers. This case nullifies the ethnic argument and any genetic or measurement trials. It is also essential to add that some researchers moved the construction date of the Octagon to the times of Emperor Augustus (27 BCE — 14 CE).
The sensational idea that the Octagon is the tomb of Arsinoë IV is still widely accepted. Even the official information board placed on-site claims, although cautiously, that "the grave was probably Arsinoë IV, youngest sister of Cleopatra and murdered at Ephesus." If the monument is the tomb of Arsinoë, this would be the only case when the remains of the Ptolemaic dynasty member have been recovered. This fact is even more surprising as this dynasty ruled Egypt for almost 300 years.
On a much down-to-earth tone, the Octagon was later reused in the 4th century CE when two letters were made public in the form of the inscriptions. The first (left) one was written in Latin by the Emperors Valentinian, Valens, and Gratian. It concerns the regulation of the public funds' division between the cities of Asia Minor heavily damaged by earthquakes. The second (right) inscription is bilingual (in Greek and Latin). Written to the proconsul, is it about the sharing of the costs of the provincial festival games among four cities. It would seem that by the 4th century, the Octagon became a kind of a public board where public notices were displayed.
This text is a fragment of a guidebook to Ephesus: "The Secrets of Ephesus".