Try 70 yards by 70 yards, whereas a hectare is 100m by 100m.
Or put another way it's 1% of a 100 acre field.
Visualising it isn't easy, like an acre of flat wheatfield is quite a bit smaller in appearance to an acre of woodland with steep gullies. That raises the question ...
On uneven ground is an acre larger or smaller on the ground than on the map? ie do you measure it as the surface lies or as a flat area? I don't know the answer to that one and it would definately be worth checking out before buying any land if it's not flat. Lawers would love that one.