Superstructure

Part of speech: noun (n.)

1. Any material structure or edifice built on something else; that which is raised on a foundation or basis; esp. (Arch.),

2. all that part of a building above the basement. Also used figuratively. You have added to your natural endowments the superstructure of study. Dryden.

3. The sleepers, and fastenings, in distinction from the roadbed.