Alexander Koryagin:   
      
   AK> -----Beginning of the citation-----   
   AK> Miss Champagne was dressed in an extraordinary mermaid outfit. It was   
   AK> green and silver with velvety sea flowers dangling from it. It had small   
   AK> teardrop shapes of net all over it, a halter neck, a very low front, and   
   AK> a circular gap at stomach level revealing Suky's emerald studded belly   
   AK> button.   
   AK> ----- The end of the citation -----   
   AK>   
   AK> Is there a rule, or consideration why we omit an article or pronoun   
   AK> before "stomach level"?   
      
   Always in such usage.  My personal theory is that the whole   
   noun phrase merges with "at" to form a compund preposition,   
   e.g.: "on top of", "at home", "in place of", but "at the   
   level of the eyes".   
      
   ---   
    * Origin: nntps://fidonews.mine.nu - Lake Ylo - Finland (2:221/6.0)