It's about as big as The Palace of Holyroodhouse
(a.k.a. Holyrood Palace) (Royal Mile, Old Town, Edinburgh, Scotland, United Kingdom) (Palace without gardens)
The Palace of Holyroodhouse, the residence of the British Monarch in Scotland, measures about 870 squares, on a total grounds area of about 4,300 squares. Each year, the Palace hosts a Garden Party, serving 8,000 guests from a 150-meter-long buffet table.
It's about as big as Seal Island
(Western Cape province, South Africa)
Seal Island, named for the tens of thousands of Cape Fur Seals that live there, measures about 870 squares. The large number seals attract great white sharks, who circle the island in a so-called "Ring of Death."
It's about four-fifths as big as a City Block (Manhattan)
In other words, 870 squares is 0.8 times the size of a City Block (Manhattan), and the size of a City Block (Manhattan) is 1 times that amount.(per Bridges, William - 1811 Commissioner's Plan for New York City) (approximate)
A Manhattan city block measures about 200 m between the Northeast-Southwest streets by about 60 m between the Northwest-Southeast streets for a total area of about 1,000 squares. There are roughly 2,000 blocks within the city, representing one of the most prolific applications of the city planning grid plan in history.
It's about one-and-three-tenths times as big as The White House
In other words, 870 squares is 1.3 times the size of The White House, and the size of The White House is 0.77 times that amount.(Washington, DC) (including wings)
Housing the presidency, the White House occupies six stories and a total of 670 squares of floor space. This space includes 132 rooms, 35 bathrooms, 28 fireplaces, and 3 elevators, as well as a tennis court, bowling alley, movie theater, jogging track, swimming pool, and putting green.
It's about two-thirds as big as Trafalgar Square
In other words, 870 squares is 0.67 times the size of Trafalgar Square, and the size of Trafalgar Square is 1.5 times that amount.(a.k.a. Charing Cross) (City of Westminster, London, England, United Kingdom)
Trafalgar Square, a public square in London, measures about 1,300 squares. m in total area. At the center of the Square is the 52 m Nelson's Column monument, built in the 1840s.
It's about one-and-a-half times as big as a Football field
In other words, 870 squares is 1.510416667 times the size of a Football field, and the size of a Football field is 0.6620689654 times that amount.(American) (per NFL regulation)
Per NFL rules, a football field should measure 109.728 m (120 yards) long by 48.768 m wide, for a total area of 576 squares. Due to a blizzard, the first NFL playoff game in 1932 was held indoors in Chicago Stadium (it was also the first indoor game) on a field measuring just 55 m by 40.0 m, for a total area of 236.80602920 squares.
It's about three-fifths as big as The Great Banyan Tree
In other words, 870 squares is 0.561 times the size of The Great Banyan Tree, and the size of The Great Banyan Tree is 1.78 times that amount.(a.k.a. The Great Banyan, a.k.a. Ficus benghalensis) (Acharya Jagadish Chandra Bose Indian Botanic Garden, Howrah, West Bengal, India)
The Great Banyan Tree is a single tree in the Indian Botanic Garden in West Bengal with aerial roots covering a total area of about 1,550 squares. While its exact age is unknown, the tree has been noted in guidebooks for over 200 years.