It really depends on whether you consider "the park" and "the surrounding area" to be two things. Or if you consider it to be a single region.
It is easier to parse this as two things so use "were". It isn't impossible to imagine someone correctly using "was".
Generally, British English speakers are more likely to follow the underlying sense (which might be singular or plural) and American speakers are more likely to follow the grammatical structure (which is plural).
Finally, if "and surrounding area" is made parenthetical, then "was" is correct. "The park (and surrounding area) was ..."