grammar - sentence formation using such and so

I have two questions:

1. I have the following sentence:

   
   
   

   
   

   "It was so extensive an area that"

   
   

   
   
   

   why do we prefer to write the above sentence instead of

   
   
   

   
   
   

   "The area was so extensive that"

   
   




2. Can we use "such" instead of "so" like:

   
   
   

   
   

   "It was such an extensive area that"