picnic area vs piece of land

picnic area and piece of land both are nouns.

Word	Noun	Adjective	Verb	Adverb
picnic area	Yes	No	No	No
piece of land	Yes	No	No	No

As nouns, piece of land is a hypernym of picnic area; that is, piece of land is a word with a broader meaning than picnic area:

Other hypernyms of picnic area include parcel, parcel of land, piece of ground, tract.

picnic area (noun)	piece of land (noun)
a tract of land set aside for picnicking	an extended area of land