Related Clues:

• Like a gateway, often
• Vaulted
• Like a 54-Across
• Curved
• Bowed
• Like some windows
• Like some eyebrows
• Like a curious eyebrow
• Like a frightened cat's back
• Like an angry cat's back
• Curved, as a sole
• Like an insole
• Colosseum entrance, e.g.
• Bowed, curved
• On the way round he had got one's back up