It's about one-and-seven-tenths times as big as a Hockey rink.
In other words, 276.4 squares is 1.69290043 times the size of a Hockey rink, and the size of a Hockey rink is 0.590702195 times that amount.(per NHL specification)
It's about three-fifths as big as Bill Gates' Home.
In other words, 276.4 squares is 0.5739 times the size of Bill Gates' Home, and the size of Bill Gates' Home is 1.742 times that amount.(Medina, Washington)
It's about half as big as a Football field.
In other words, 276.4 squares is 0.4798611111 times the size of a Football field, and the size of a Football field is 2.083936324 times that amount.(American) (per NFL regulation)
It's about two times as big as Fort Knox.
In other words, 276.4 squares is 2.18 times the size of Fort Knox, and the size of Fort Knox is 0.459 times that amount.(a.k.a. the United States Bullion Depository, a.k.a. "Gold Vault") (Kentucky)
It's about two-fifths as big as The White House.
In other words, 276.4 squares is 0.41 times the size of The White House, and the size of The White House is 2.4 times that amount.(Washington, DC) (including wings)
It's about three-tenths as big as a City Block (Manhattan).
In other words, the size of a City Block (Manhattan) is 3 times 276.4 squares.(per Bridges, William - 1811 Commissioner's Plan for New York City) (approximate)
It's about five times as big as a Basketball court.
In other words, 276.4 squares is 5.180880975 times the size of a Basketball court, and the size of a Basketball court is 0.1930173661 times that amount.(per NBA regulation)