Historical clue formulations

• Deep defenses — 2025-05-10
• Siege deterrents — 2024-12-07
• They're found around castles — 2023-05-10
• Strategic bodies of water — 2022-01-07
• Deep defenses — 2018-05-13
• Rings of water around castles — 2018-01-01
• They're crossed by bridges — 2012-03-14
• Things that drawbridges bridge — 2010-07-18
• Tokyo Imperial Palace features — 2010-07-09
• Castle-defending ditches — 2010-05-10
• Siege deterrents — 2004-01-30
• Zoo dividers — 2002-09-15
• Castle protectors — 2002-04-16
• Obstacles for marauders — 1999-03-14
• Zoo barriers — 1998-10-22
• Deep ditches — 1998-10-18
• Castles' barriers — 1998-03-02
• Drawbridges cross them — 1996-02-20
• Protective rings — 1994-10-30