Task: Question Answering
Input (English): Passage: Structure 12 lies to the east of Structure 11. It has also been excavated and, like Structure 11, it is covered with rounded boulders held together with clay. It lies to the east of the plaza in the southern area of the Central Group. The structure is a three-tiered platform with stairways on the east and west sides. The visible remains date to the Early Classic but they overlie Late Preclassic construction. A row of sculptures lines the west side of the structure, including six monuments, a stela and an altar. Further monuments line the east side, one of which may be the head of a crocodilian, the others are plain. Sculpture 69 is located on the south side of the structure.Structure 17 is located in the South Group, on the Santa Margarita plantation. It contained a Late Preclassic cache of 13 prismatic obsidian blades.Structure 32 is located near the western edge of the West Group.Structure 34 is in the West Group, at the eastern corner of Terrace 6.Structures 38, 39, 42 and 43 are joined by low platforms on the east side of a plaza on Terrace 7, aligned north–south. Structures 40, 47 and 48 are on south, west and north sides of this plaza. Structures 49, 50, 51, 52 and 53 form a small group on the west side of the terrace, bordered on the north by Terrace 9. Structure 42 is the tallest structure in the North Group, measuring about 11.5 metres (38 ft) high. All of these structures are mounds.Structure 46 is a mound at the edge of Terrace 8 in the North Group and dates from the Terminal Classic through to the Postclassic. The west side of the structure has been cut by a modern road.Structure 54 is built upon Terrace 8, to the north of Structure 46, in the North Group. It is surrounded by an open area without mounds that was probably a mixed residential and agricultural area. It dates from the Terminal Classic through to the Postclassic.Structure 57 is a large mound at the southern limit of the Central Group with an excellent view across the coastal plain. The structure was built in the Late Preclassic and underwent a second phase of construction in the Late Classic. It may have served as a look-out point. 
Question: Which structure  may have served as a look-out point?
Output (English): Structure 57.