Related Clues:

• Event with a horse
• Use a springboard
• Geraldo Rivera opened one in 1986
• Strongroom
• Leap over the underground chamber
• Lower ground floor
• Lowest floor of a building
• Jump over a crypt? (5)
• Lowest floor
• Man beset in bottom of house
• Beats men up in cellar
• Room at the bottom
• A floor below ground
• What the computer does with H.R.H. when he's not at home, by the sound of it
• Get over what's under