The East Baths is one of the two bath complexes at Andriake; it was uncovered and conserved during the campaigns of 2011 and 2012. It is important because it provides us with a complete example of Early Byzantine baths, about which almost nothing is known in the region. For with its Roman phase it adds new information on the regional baths as well as reveals new de-tails in addition to what is known regarding bath planning. The excavation discoveries and our interpretations are hereby presented to the academic world.The building is the first Roman building at the eastern fringe of the southern settlement in Andriake. It is located in the social part of the Roman-period harbour settlement. Along the coastline extending to its west are commercial areas. The relation between commercial and social areas is well planned with respect to urbanism. The social needs of Andriake were sup-plied in the area starting with the East Baths and going westward up to the Agora encompass-ing two social structure groups and the West Baths. West of this area is the commercial area encompassing the Harbour Agora and Granarium in the centre. The quay street extends all along these buildings on the coastline. Here the Byzantine urban system is almost the same as the Roman-period one. That there are even two baths in the Andriake in addition to the main baths in the main city of Myra clearly shows the high traffic of the harbour. Thus visitors to the harbour did not have to go to Myra for bathing and similar needs.ArchitectureRooms I and II were the frigidarium and apodyterium; rooms III and IV the tepidarium; rooms V and VI were the caldarium. Rooms I and II do not have any interconnection and heating, but they functioned together. Rooms III, IV, V and VI have a heating system installed beneath the floor and in the walls. Plan and technical features of the baths during the Roman and Early Byzantine phases need to be studied separately. There are two baths resting on the same plan basis, but their plan characteristics are different; nevertheless, their technical features are quite close to each other. After the Roman-period baths some sections were cancelled while others were added, thus creating the Byzantine baths with a different layout. As for dimensions, the Roman baths was 197 sq. m. while the Byzantine one was 175 sq. m. Most of the rooms other than the caldarium were used during both phases.In the Roman phase the layout is quite familiar with rectangular rooms placed side by side along the north-south axis. The water supply, wastewater drainage and heating system reflect Roman-period technical practices. In layout, as most of the Roman baths continued in use dur-ing the Byzantine period, no peculiar design came up. Additions to the plan are practical, thus random. It can be said the main construction in the Byzantine period was the caldarium added to the west and the depot serving the praefurnium annexed to the caldarium. DatingAs the building remained in use, small finds recovered belong to the Byzantine period and are dated to the 5th-6th centuries A.D. Most of the coins are from the 6th century. These dates reveal the upper limit of use during the Byzantine period as the beginning of the 7th century. The coin and potsherds of the 11th century uncovered in the baths belong to a period when the baths lost its function and served other purposes. Dates of the reused materials also match with the possible falling dates of Andriake's churches. During the 4th-6th centuries six churches and these two baths served the needs of the Christian inhabitants and other visitors of commerce or pilgrimage. The Roman phase ended possibly in the late 4th century, but the baths remained in use during the next phase with revisions and additions. The building seems to have remained in use during the 5th century with small repairs. The actual Byzantine phase starts when the late caldarium was built after the earthquake of 529 during the reign of Justinian I. It is known that Myra and Andriake were also affected from this earthquake that hit central Lycia in 529. Thus especially the caldarium, which had fallen out of use, was rebuilt after the earthquake, and the baths remained in use with this new layout until early 7th century. Based on the fact that the West Baths was built earlier as it was closer to the centre, the East Baths was built later due to high demand. So at the earliest the 3rd century can be proposed for the Roman phase of the East Baths. In conclusion we suggest these periods for dating the baths: the 4th century for the Late Roman phase; the 5th century for the phase when the Roman bath remained in use in the Byzantine period; and the 6th century for the Byzantine phase when the early caldarium was destroyed by an earthquake and the new caldarium was added.In the course of rebuilding the doorway leading from the tepidarium to the caldarium in the Roman phase and air channels in between were blocked. Instead a doorway was opened from the tepidarium to the new caldarium on the west. It is thought that when Myra became the capital of Lycia during the reign of Theodosius II (r. 408-450) Andriake became the main harbour of the region. Thus extensive constructions were made. It is likely that the Byzantine phase of the East Baths was revised, renovated and stayed in use until the earthquake. When it was rebuilt after the earthquake during the reign of Justinian I, the baths remained in use for another century. That the great majority of coins and other small finds date to this period supports the last phase of use. With the decline of civilization here due to Arab raids, further construction was no longer possible, and the central harbour area was transformed into a poor quality settlement beginning in the 7th century.