The Mayor arrived and unexpectedly found a sea of tents in front of City Hall.
a sea of – an expression used when several objects cover a surface as far as the eye can see.
Huddleston, Rodney and Geoffrey K. Pullum."Catenative complements, adjuncts, and coordinates: Adjuncts of result" The Cambridge Grammar of the English Language. Cambridge: Cambridge University Press, 2002 (1224) Print.