Related Clues:
- Structure carrying road or railway over a valley
- Support for a travelling crane
- Supporting framework
- Span across a gorge, say
- Support for overhead work
- It' s under way, possibly, across the valley
- Support for crane
- Rocket launch tower
- Support for, eg, crane
- Travelling crane support
- Overhead structure for such as crane
- Long arched structure
- Overhead supporting structure
- Long road/rail bridge
- Overhead structure, massive one near railway that I avoided