Doris Salcedo, Installation at International Istanbul Biennial, Salcedo's idea was to create a "topography of war"--not tied to a specific historical event, but to war in general. wooden chairs piled high between two buildings in central Istanbul.
William Forsythe Scattered Crowds 2012 thousands of white balloons are suspended in the air accompanied by a wash of music “the air-borne landscape of relationships, distance, of humans and emptiness, of coalescence and decision”
Argentinian artist Leandro Erlich created this illusion of people walking underwater called The Swimming Pool, for The Century Museum of Contemporary Art in Kanazawa, Japan. It's a piece of glass with water on top of it, and empty space on the bottom.