Two women in billowing dresses smash a shuttlecock at each other, giggling when one trips over a picnicking family sprawled out on the grass.
Nearby, skinny youths boot a soccer ball around, while an attractive young couple, looking deeply into each other's eyes, whisper earnestly on a bench.
It is Thursday night, and the Jamshidieh park in north Tehran is thronged with people enjoying the beginning of the Islamic weekend.
There is a carnival atmosphere. Good-natured crowds ebb and flow along paths that climb the steep, laboriously landscaped hillside park.
The air is sweet with the scent of jasmine and honeysuckle. Cooling streams trickle alongside the paths, carrying snowmelt from the Alborz mountains, which loom over northern Tehran, glimmering in the moonlight.
The Iranian capital has many wonderful parks - their trees, lawns, and magnificent flower beds carefully tended by armies of municipal workers. Millions of dollars have been invested in recent years to provide these oases of cool and pleasant greenery for Tehranis.
Parks are a place to socialize and a welcome respite from frequently cramped apartments in this noisy, teeming, and often-polluted city of 12 million.
They also offer an inexpensive form of entertainment in a city where 40 percent of the people live below the poverty line, according to official figures, and only the well-off can afford houses with gardens.
In addition, parks provide an alternative to Western forms of entertainment, such as bars or nightclubs, which are unavailable because alcohol and dancing in mixed company are banned under Iran's Islamic law.
In the past, young Iranians who tried to flirt in parks would have to play a cat-and-mouse game with morals police, whose job it was to ensure that public behavior conformed with Islamic strictures. Women wearing too much makeup risked arrest.
But the social atmosphere has thawed remarkably since reformist President Mohammad Khatami, came to power four years ago, promising greater personal and political freedom. Couples feel safe to date discreetly in parks and other public places, while women are free to wear more cheerful colors. The head scarf remains mandatory in public, but it is inching back inexorably.
Any security presence in the parks, especially after dark, is aimed mainly at combating drugs. The authorities announced in July that nearly 12,000 addicts and dealers had been arrested in a week-long, nationwide police crackdown.
Drug abuse is seen as Iran's biggest social problem. There are 1.2 million serous addicts, but some experts believe as many as 6 million of the country's 63 million people take drugs for recreation.
Tehran's police chief, Mohsen Ansari, warned recently that the capital's public gardens had become haunts for dealers and addicts. But the police are determined to keep Tehran's parks free of drugs.
In summer, many families cook their food at home and bring it in pots and pans to enjoy in the neighborhood park. Western tourists are surprised by the hospitality of even the poorest Iranian families, who offer to share their dinner with passing strangers from other countries.
But in greeting Iranians, foreign men should be careful not to embarrass their hosts by attempting to shake the hands of Iranian women, while women must also be careful not to attempt the same with an Iranian man.
To do so is taboo under Iran's Islamic customs, although Westernized Iranian women, particularly in private, will insist on shaking a male friend's hand.
Picnics for the less well-to-do often consist of just cucumbers, bread, and tea - consumed while family members lounge on the grass or sit on park benches.
Many restaurants, however, also cater to those on tight budgets: A lamb, chicken, or beef kebab; dish of rice; and a side salad can cost as little as $2 or $3.
Iranian food is inventive, rich and varied. Rice - usually flavored with saffron - is a staple, along with vegetables.
The dishes that have made Persian cuisine famous worldwide are mostly homemade, because Iranian women generally do not work in restaurants.
One of the most celebrated dishes is ghormeh sabzi, a subtle concoction of lamb, herbs, and lemon that takes great skill and hours to prepare. Another is sesenjan, chicken in a pomegranate sauce with walnuts.
Iranian food is not spicy. Herbs are used a lot, as is fruit - from plums and pomegranates to quince, prunes, and raisins.
Much preparation time also goes into rice. "It is a whole ceremony," says Somaya, an Iranian friend of mine.
Iranians feel that the best rice is a type grown in the northern part of their country around the Caspian sea; it costs twice as much as the imported varieties from Southeast Asia.
First, it is thoroughly rinsed. "We do this because we believe that the smell of the bag or container it was in could destroy the beautiful scent of the Caspian rice," says Somaya. The rice is then put in boiling water, strained, and finally steamed.
At most restaurants, the kebab is king, mostly because it is fast to prepare, and eateries are generally run by men, whose main culinary skill, as for many of their Western counterparts, is barbecuing on the grill.
However, in recent years many fine restaurants have introduced the best home cooking, which is a hit not only with Iranians but with foreign tourists, including Americans, who are visiting this exotic and hospitable country in steadily rising numbers. There is also no shortage of Western-style fast-food outlets - popularized during the regime of the shah - which offer burgers and pizzas.
Food is washed down with tea, soft drinks, or tangy, fresh fruit juices, such as pomegranate, cherry, apple, and pear.
Baby-sitting is never a problem for Iranians. Unlike in Western societies, children go out evenings with their parents and stay up late.
The family is the basis of social life in Iran. While men in other Middle Eastern countries go out with male friends on weekend nights, Iranian men take out their families.
Every restaurant is a family restaurant. Even in the most expensive establishment, no diner would dream of giving parents a disapproving look for bringing their children. It is not unusual for waiters with a few spare moments on their hands to play with boisterous toddlers so that the parents can enjoy their meal.
Traditional teahouses aside, the Jamshidieh park has six restaurants, each serving cuisine from a different part of the ethnically diverse country.
Even at 11 p.m., Tehran's parks are full, the swings and merry-go-rounds alive with the shrieks of delighted children. Vendors do a roaring trade selling balloons, inexpensive toys, soft drinks, and ice cream.
Come midnight, there is a sight which Western countries generally experience only before and after work: rush hour.
The streets of Tehran are clogged with traffic as families finally leave the parks and head for home.