A city park is a piece of dated argument about what a city owes its residents

Most old parks were not built as parks

A large share of the green space in older cities began as something private: a royal hunting ground, an aristocratic estate, a monastic garden or a common grazed by people with grazing rights. These became public through purchase, confiscation, gift or slow encroachment, and the original purpose is usually still visible in the shape.

Hunting grounds are large, irregular and full of long straight rides designed for riding rather than strolling. Estates have a house somewhere in them, or the ghost of one, and a lake positioned to be seen from its windows. Commons are flat, edgeless and lack any central feature at all, because nobody designed them.

This matters because it explains the odd distribution of green space in most European cities. Parks are where an aristocrat happened to own land, not where the population happened to need somewhere to sit, and the districts that grew up in the nineteenth century without a nearby estate frequently have nothing at all.

The nineteenth-century park was public health policy

The great wave of deliberately built municipal parks came with industrial cities, and the argument for them was explicitly about health, air and moral improvement rather than about recreation as we would now describe it. They were built to be walked through slowly, in respectable clothes, by people who had spent the week indoors.

The design language follows the argument. Winding paths that make the ground feel larger, a bandstand, a lake with a boathouse, formal bedding near the entrances, specimen trees labelled for instruction, gates that were locked at night, and a lodge for the keeper who locked them. Almost every city of that period has one and they are recognisable anywhere.

They also came with rules, and the rules are the giveaway. Keep off the grass, no ball games, no dogs, no trading: the park was conceived as an outdoor room to be looked at rather than used, and much of the conflict over these spaces since has been about relaxing exactly those restrictions.

The twentieth century put the emphasis on activity

Later parks and later reworkings of older ones assume people want to do something. Pitches, courts, running tracks, paddling pools, skate areas and children’s playgrounds take space that a Victorian designer would have given to planting, and the paths straighten because they are being used to get somewhere.

Postwar planning also produced a great deal of green space that is not really park at all: the grass between blocks of flats, the verges beside a ring road, the buffer strip along a railway. It is open, it is green, and it is often almost entirely unused, because nothing about it invites anybody to stop.

The distinction between designed park and leftover green is one of the more useful things to notice while walking a city. Both appear the same colour on a map, and only one of them is doing any social work.

Recent parks are usually built on something that failed

The current generation of urban parks tends to occupy disused infrastructure: a closed railway, a filled dock, a decommissioned airfield, a covered river, a demolished industrial site. That origin gives them their characteristic linear or awkward shapes, and it is why so many of them are long and thin.

These are expensive to make and expensive to keep, because contaminated ground has to be dealt with and because the planting is often ambitious. They also tend to be very successful, which brings its own difficulty: a well-used new park raises the value of everything around it, and the residents it was justified by are not always the ones who end up living there.

That tension is genuinely unresolved. The argument that green space should go where deprivation is greatest and the observation that new green space reliably raises rents are both correct, and cities have not found a clean way through it.

Reading a park in the first ten minutes

Look at the edges first. A park with many entrances and soft boundaries is used as a route by people going about their day, and it will be busy at commuting hours. A park with a wall, three gates and a closing time is used as a destination, and it empties completely in the evening.

Then look at who is in it and at what time. Weekday mornings belong to parents, older residents and dog walkers; lunchtimes to whoever works nearby; weekends to families and organised sport. A park with only one of these populations is telling you something about the district around it.

And notice what the city has decided to provide free: benches, shade, drinking water, a public toilet that is actually open. Those four are the difference between somewhere people pass through and somewhere they spend an afternoon, and they cost far less than the flower beds.