EUROPE'S urban open spaces should not be merely passed through, en route to the next landmark, event or meal. They deserve to be savored for what they can tell us about the form and texture of other lives -- and for the sheer delight of participating in their bracing diversity.

Some of Europe's most memorable urban places are not necessarily distinguished by their design, their architecture or their history so much as by their function -- or simply the strong emotional response they evoke. The following five open spaces remain, for me, touchstones of uniquely European ambience. Each has been classified according to the experience.

Spectacle: Whether you are among the fortunate 33,000 viewers who have seats, or part of the 30,000 who stand, the annual Pailo horse race on July 2 or Aug. 16 in Siena's Piazza del Campo provides a rare order of theater. The horses race three times around the square, which is specially prepared for the event with a thick layer of earth and mattresses placed against the walls to save the necks and limbs of thrown jockeys. Ten "contradi" or teams compete in the race, and their traditional emblems and colors, their grand procession into the arena, the flag tossing and the blessing of the horses have changed little from the first race in 1656.

But throughout the rest of the year, and even when completely empty, the Campo evokes a potent sense of drama. It is one of the great stages of the world. Originally a steep and eroded valley-head, the sloping square is divided into nine brick-paved sections, each separated by radiating stone strips from the Palazzo Publico at the bottom. Since 1262 the Italian city has regulated development and design of the square and all the adjacent buildings, to frame the open space. It looks and feels like the head of a valley, and when you reach the Campo, after having walked the narrow streets of Siena, its enormity, openness, brightness and view of the sky provide a breathtaking sensation. Talk ceases and you stand and stare, as if waiting for a curtain to rise.

Serenity: The Cathedral Green at Wells, England, is a grassy precinct surrounding the Wells Cathedral, built between 1220 and 1239 and often considered the most architecturally interesting in the country. Wells may be the most perfect, least-modernized example of a medieval cathedral city in England, and its unhurried pace of life invokes a profound sense of calm and reflection. One truly leaves the 20th century behind upon entering the cathedral grounds. To savor the quiet, you can wander about the grassy enclosure, take a look at the parish houses, and even book lodgings at the cathedral's ancient Gate House, now a hotel. Almost 700 years old, the house has a 60-front frontage on the green where tea may be taken in the shade of a stately lime tree.

Animation: No open space is more vibrantly alive than the plaza facing the Pompidou Center of Paris. The Center's architecture and scale, its suitability as a symbol of the cultural ascendancy of France, and its outrageous inside-out mechanical systems have fueled heated debate since its opening in 1977. Its one indisputable success is its plaza, which has become the stage for an amazing vartiety of professional and amateur street performers.

The square is huge, larger than the area covered by the Center. From midmorning to dark, the square features mime groups, jugglers, fire-eaters, broken-glass walkers and rollers, singers, magicians, and theater troupes. The human bouillabaisse also includes pamphleteers and speakers of all political persuasions, vendors, hustlers and pickpockets.

On Saturdays and Sundays large parts of the square are taken over by North African emigres as gathering places for conversation and comradery. Most have come to France without their wives or families seeking higher wages. The square is their weekend living room. The biggest crowds gather around those playing musical instruments, and when the occasional woman is persuaded to dance, the circle swells to hundreds of clapping men, mostly dressed in black or dark gray, thinking, probably, of home. It is the best free show in Paris.

Courting: A prime function of public space in Europe is to provide a setting for the rituals of romance. Few places are better suited for courting than the medieval town square and connecting pedestrian streets of Zadar, Yugoslavia.

A town founded by Roman legion veterans about 100 B.C., Zadar was ruled by Byzantines, Venetians, Italians, Austrians and the French before the Yugoslav nation was formed. It boasts handsome remains of most of its 2,000-year history, including the ruins of a Roman forum. But what I find most fascinating about Zadar is the local courting custom called korso.

At sundown, beginning at the tra narodni (central square) and branching out in a rectangular pattern on to connecting pedestrian streets, groups of girls dressed in their finery walk arm in arm. Young men, similarly spruced up, walk likewise, arm in arm or in groups. Everyone walks in the same direction around the square and its circuit of streets. A bit later, families appear, with children walking or in strollers. Every window or bench is occupied by the elderly, who, if they can't walk, look. After about an hour, everybody changes direction and walks the circuit facing the other way. Generally the korso is over in about two hours. It offers the whole town a leisurely opportunity to greet one another, gossip and air relationships. But in particular it provides an acceptable way for boys to see girls, and vice versa.

Strolling: Taking evening walks is a fairly universal European pastime. Once of the best strolls is along the Ramblas in Barcelona. I suggest starting on the upper Ramblas, at Paseo de Gracia north of the Plaza Catoluna, and walking south toward the old town and the harbor.

This stretch of the 60-foot-wide pedestrian way is quite different from the lower part of the Ramblas. It is a mixed business and residential area, with only an occasional sidewalk cafe and no street vendors. But it is a handsome, elegant section with Gaudi-designed street furniture, fashionable clothing stores, galleries, and offices. The flower plantings along the walkway are more ornamental and better maintained than lower on the Ramblas.

Reaching the bottom of Paseo de Gracia, you cross the Plaza Catoluna and find the active section of the Ramblas. The walking surface here has a wavy pattern of alternative black and white bands. Mature trees are planted on either side of the space, partially screening out the single lane of traffic that borders each side of the Ramblas. Handsome street lights, kiosks and subway-entry pergolas liven up the streetscape.

But it is the movables that are exciting: First, the endless parade of people, young and old, poor and rich, sober and drunk, tourist and local, gay and straight, moving up and down the Ramblas until 4 a.m. in the morning. Second, almost every type of movable chair -- plastic, wooden, and aluminum -- can be rented for people-watching. All the restaurants along the Ramblas are located across the street; to get to the sidewalk cafes, waiters have to constantly dodge traffic. The other movables are the vendors. Certain stretches of the Ramblas seem reserved for similar products -- birds, cactus plants, cut flowers, food, household goods, magazines and books. The vendors line both sides of the strip, and the system appears to be the essence of a free-market enterprise. But vending is highly organized by municipal code and each space is numbered with taxes paid to the city.

This part of the Ramblas goes on through the historic quarter of Barcelona, where narrow, winding streets will lead you off to some of the city's great restaurants. The last stretch, as you approach the harbor, leaves the cafes and vendors behind and becomes active on weekends as a craft sales area for artisans.