Possible Clues:

• Sounds as if the whole of this is in rock to go up and down at the bottom
• Must set about river, which is underground
• Cave that's unattractive changed at last
• Got about decay in recess
• Cave in which British and German kings meet
• About the end of December reached Santa's base
• Artist's just right for one picturesque cave
• May sound holy in rock to go up and down at last
• Fancy cave
• Sounds as if the whole of this is in the rocks