Another mosaic building was uncovered during the field season of 2011. It was located in sector 4 of the excavation area, at the eastern edges of the lower part of the ancient city of Apollonia. A north-south/south-west wall (US 1116) was revealed in the northern side of the sector. This wall was 80 cm wide; it was made of reused sandy stone blocks (on its eastern and outer face) and bricks bonded with mortar (on the western and inner side). Parallel and next to the outer side of the wall, an open drainage channel (US 1150) was discovered. It was made of bricks and had a maximal width of 25 cm. Slightly beyond it, the excavations revealed a 6, 10 m wide road (US 1154) paved with gravel and pebble stones. The road follows the same orientation as the other roads discovered in the habitation quarter of the lower part of the city. Two phases of construction were noticed in wall 1116: the sandy stone line is duplicated by another new brick wall, which covers the edge of the mosaic floor and continues toward the west. Two other parallel walls, perpendicular to wall 1116 (abutting the brick courses or cut through the sandy stone blocks of the wall) relate to the second phase of construction. The first was 62 cm wide and was built of whole bricks (US 1121), the second (US 1170 - 44 cm wide) of fragmented bricks. This situation suggests rearrangements made to the inner spaces of the structure. The mosaic floor however, remained in use. Two other walls (US 1185 and 1186), which continue perpendicular to wall 1170, and cut the mosaic floor, seems to belong to a third phase of construction. The mosaic is made of squared limestone tesserae, each side of 1, 2 cm long. The remains show an identically repeated decorative image. The edge of the mosaic floor, which extends along the wall 1116, is decorated with braid patterns, bordered by an outer frame (34 cm wide) of two parallel black bands. The braid consist of two strands which are intersected with each other: one made of three threads of yellow, black and white tesserae; and the other of two threads of red and white colours. The red thread is wider then the others as it consist of two lines of tesserae. The decorative motifs, which are bordered by the frame of white and black tesserae, represent a four petals flower, traversed in its outer and inner sides by two circles, forming in this way a cross and a rectangle at the intersection point of these geometric figures. The rectangule consists of four tesserae of back and red colours; the extremity of each petal is divided by a black tessera. The main image of the mosaic motive is of repeated circles, intersected at their centre, and at each time distinguished by tesseare which divide the edges of the four flowers. The coins discovered during the excavation aided in defining the chronology of the mosaic building: two coins, one of the Emperor Aurelian and the other of Probus, identified on the mosaic floor, define the last phase of use of the building; whereas the coin of Constantine found in the destruction layer, shows the same situation as revealed in the other structures of this part of the city, and dates to the end of the 3rd Century AD. The construction date of the building remains as yet undefined; however if considering the mosaic style it might date to the 1st -2nd centuries AD. The mosaic surface discovered so far is 4 m wide, exceeding the sizes of the peristyle houses of Apollonia. It suggests a large public building, probably a basilica.