A description of a visit to the Lascaux Caves yields this celestial simile for a soaring natural roof. 

The first room, called the room of the bulls, has a beautiful natural vault, as though constructed from frozen clouds. 

Source: Zbigniew Herbert, Barbarian in the Garden, trans. Michael March & Jaroslaw Anders (New York: Harcourt Brace & Company, 1985), p. 8

Photo credit: klickblick at pixabay