It's about as big as a City Block (Manhattan)
(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 hectares. 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-one-fifth times as big as The Palace of Holyroodhouse
In other words, 1 hectares is 1.2 times the size of The Palace of Holyroodhouse, and the size of The Palace of Holyroodhouse is 0.83 times that amount.(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 0.810 hectares, on a total grounds area of about 4 hectares. Each year, the Palace hosts a Garden Party, serving 8,000 guests from a 150-meter-long buffet table.
It's about one-and-one-fifth times as big as Seal Island
In other words, 1 hectares is 1.2 times the size of Seal Island, and the size of Seal Island is 0.83 times that amount.(Western Cape province, South Africa)
Seal Island, named for the tens of thousands of Cape Fur Seals that live there, measures about 0.810 hectares. 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 Trafalgar Square
In other words, 1 hectares is 0.83 times the size of Trafalgar Square, and the size of Trafalgar Square is 1.2 times that amount.(a.k.a. Charing Cross) (City of Westminster, London, England, United Kingdom)
Trafalgar Square, a public square in London, measures about 1.20 hectares. 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 seven-tenths as big as The Great Banyan Tree
In other words, 1 hectares is 0.694 times the size of The Great Banyan Tree, and the size of The Great Banyan Tree is 1.44 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 1.440 hectares. While its exact age is unknown, the tree has been noted in guidebooks for over 200 years.
It's about one-and-three-fifths times as big as The White House
In other words, 1 hectares is 1.6 times the size of The White House, and the size of The White House is 0.63 times that amount.(Washington, DC) (including wings)
Housing the presidency, the White House occupies six stories and a total of 0.620 hectares 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 three-fifths as big as The Biltmore Estate
In other words, 1 hectares is 0.613 times the size of The Biltmore Estate, and the size of The Biltmore Estate is 1.63 times that amount.(Asheville, North Carolina) (house only)
The main house of Biltmore Estate covers 1.630 hectares and contains 250 rooms. The fifty-six auxiliary buildings of the estate are interconnected through the nearly 71 km of roads on the Biltmore grounds.