Related Clues:
- It could fall on a foot
- Vault feature
- Viaduct feature
- ''Duke'' starter
- Impressive entrance
- Tongue-in-cheek
- Design feature of many a viaduct
- Bend over backward
- ___ of Constantine (landmark in 45-Across)
- It's big in St. Louis
- Rock formation
- St. Louis symbol
- Roman construction element
- Lift, as one's brow
- Eyebrow or rainbow