The structure has 21 arches with spans of 15 m ( 49 ft ) and reaches a height of 30 m ( 100 ft ) above the valley .
The structure is built entirely out of concrete .
The structure , which is built entirely out of concrete , has 21 arches with spans of 15 m ( 49 ft ) and reaches a height of 30 m ( 100 ft ) above the valley .