Historical clue formulations

• Like eyebrows — 2022-01-22
• Colosseum entrance, e.g. — 2011-05-29
• Like a 54-Across — 1999-09-05
• Like a gateway, often — 1997-12-02
• Vaulted — 1995-04-14
• Like many doorways — 1994-01-02