In the USA, considerable study has been given to the size of public squares. The general conclusion is that the diameter of squares should not exceed 70 feet, except in places that are great town centres, teeming with people, like Trafalgar Square or the Piazza San Marco. The findings are based on the distances at which people can comfortably recognize or hear each other. Two people with normal vision can see each other clearly up to 75 feet. They can also communicate up to this distance, even though their voices may be raised. This may mean that people feel half-consciously tied together in squares that have diameters of 70 feet or less, where they can make out the faces and half-hear the talk of the people around them. Architects are thus now recommended to make public squares no more than 45 feet to 60 feet across, certainly never more than 70 feet.