Historical clue formulations

• Explore a cave — 2025-07-24
• Go caving — 2024-12-05
• Explore caves — 2021-03-15
• Do some underground exploring — 2019-12-26
• Go caving — 2014-04-17
• Go caving — 2010-07-16
• Cave — 2009-02-20
• Explore caves — 2004-11-11
• Go caving — 2003-09-12
• Explore caves — 1997-06-19