Sentence:  To reinforce , and sometimes to replace , the simulated typography , Braque and Picasso began to mix sand and other foreign substances with their paint ; the granular texture thus created likewise called attention to the reality of the surface and was effective over much larger <WSD>areas</WSD> . 
Meaning of the word marked with <WSD> tags:  a particular geographical region of indefinite boundary (usually serving some special purpose or distinguished by its people or culture or geography)