public square vs piece of land

public square and piece of land both are nouns.

Word	Noun	Adjective	Verb	Adverb
public square	Yes	No	No	No
piece of land	Yes	No	No	No

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

Other hypernyms of public square include parcel, parcel of land, piece of ground, tract.

public square (noun)	piece of land (noun)
a place of assembly for the people in ancient Greece	an extended area of land
an open area at the meeting of two or more streets