Mayor Is Olympics’ No. 1 Security Guard : Spain: As the architect of his city’s bid for the Games, Pasqual Maragall is determined that nothing spoil their second half.

Over breakfast at City Hall, an aide brought Mayor Pasqual Maragall what sounded like good news: In the absence of any foreseeable threat, the daily security bulletin by anti-terrorist experts protecting the Olympic Games was shrinking, day by day.

“That’s the problem,” Maragall snapped. “We must fight not to let this become a routine. We’ve got to keep up the tension.”

Barcelona is slightly more than halfway home as host to the athletic world. Maragall, who was architect of his city’s bid for the Games and is chairman of the organizing committee, likes what he has seen--so far.

“We are at cruising altitude. The machine is oiled and working well,” Maragall said during the middle weekend of the Summer Olympics.

The Games began on a civic burst of excitement fueled by adrenaline. But now, officials say, there are signs that fatigue is setting in, compounded by climate.

Mediterranean summer is not for sissies. The heat--nearly 100 degrees day after dry day--is sapping. Hot, still nights make sleeping difficult in a city where 97% of homes are without air conditioning.

Attention wanders. A young security guard at the Games asks himself: Do we really have to go through the hassle of passing everyone through a metal detector every time? Does a terrorist wonder: Is now the time?

To counter any across-the-board letdown, Maragall and other organizers are urging what they like to call the “Olympic Family” to alertly stay the course.

One more week.

A high-tech coordination center in City Hall takes the municipal pulse in real time. One surprise: Despite the constant Olympic comings and goings, there is 25% less traffic in the city than one year ago.

Part of the decline is because Barcelonans tend to begin their summer vacations in the last week of July. But many local residents have been scared away from driving downtown by Maragall’s unabashed intimidation, by stiff Olympic parking fees and by omnipresent tow trucks that bagged 481 cars in a single day last week.

But even as remote cameras at 33 key intersections beam pictures of clear sailing, the center computers say Barcelona is full.

Subway traffic is up 15.7%. Garbage collections have jumped to 2,035 tons a day compared with 1,780 tons a year ago. Hotel occupancy is running at 97.8%, compared with 41% a year ago. And visitors are interested in more than sports: Daily attendance at the Picasso Museum is averaging 2,200, double that of a year ago.

City police officers have been brought out of retirement to be navigators for bus drivers brought from all over Spain to knit the Games together. To the fury of Barcelona’s taxi drivers, Olympic buses link five villages, 10 centers and 69 venues on 267 different routes. There is no charge to any of the 120,000 credentialed members of Barcelona’s extended summer family.

Even after the first week, though, access problems abound. “VIPs tend to have deep hierarchical sentiments. They don’t like 18-year-olds telling them where they can and cannot go,” Maragall said.

The mayor is quick to respond to complaints: He got a more varied diet for volunteers and security personnel in the Olympic Village after they began sending him electronic mail complaining that they could not endure a planned 16 consecutive days as guests at the same hamburger restaurant.

But Barcelona’s can-do mayor will not, he said with a smile, take any heat for the heat: “In this country, we still do not build houses with air conditioning. I don’t have any at home. Why should we have installed it for the athletes and the press?”

And neither is he losing any sleep, while averaging about five hours a night, over how expensive everything is. When Barcelona began planning for the Games in 1986, he noted, $1 bought 165 Spanish pesetas.

Today $1 is worth about 90 pesetas. And every cup of coffee is a new adventure in extortion.

Still, despite six years of planning, the 51-year-old Maragall, a city planner by trade, says there are things he’d do differently if Barcelona had to do them over again.

“If I was planning for the ’96 Games in Atlanta, I’d try to make the separation between the villages and ordinary streets with something other than chicken wire. A city means communications, and our wire is also ugly to look at,” he said.

One reason that Maragall and executives of the Barcelona Organizing Committee want people on their toes throughout the second half of the Games is that there is a lot that can still go wrong.

There is still the threat of terrorism, which dominates security concerns today as much as it did when the Games were still on the drawing board.

Maragall understands too well that one bad security mistake in an otherwise letter-perfect Olympics might be all anybody remembers about Barcelona in 10 years.