The city basilica of Tlos measuring 84 x 33 m laid out on an east-west axis echoes the typical cross-shaped planning scheme of the Anatolian basilicas. The interior was divided into three units through a line of columns: one central nave flanked by aisles. The eastern end of the nave is apsidal with openings. The spaces between the columns within the basilica were closed with walls built of bricks and spolia, although some openings were left in order to link the central nave with the side aisles. It seems that the nave and the side aisles in the interior were divided into smaller units in the subsequent periods. Some parts of the interior of basilica were also used as a burial ground. Eight windows opened in the northern and southern walls and two in the eastern wall provided the basilica with the necessary light. The traces of plasters with painted decorations observed on the interior walls indicate that the interior of the basilica was originally fully plastered. The floor of the basilica was covered with mosaics of geometric designs. Although the basilica was first built in the Early Byzantine period, the earliest extant remains date to the Middle Byzantine period. A small chapel attached to the southern wall of the basilica represents the last architectural phase of the building.