Six years after its opening ignited a baseball renaissance in what had become a football city, it turns out that Citizens Bank Park's most significant feature may not be the unexpected wind patterns, the brick-and-exposed-steel facade, the swaying Liberty Bell, or a playing field 23 feet below street level.

Instead, it might be the drink rails, those tables for standees behind the lower-level seats. Designed merely to protect those in back rows from spilled soda and mustard, they quickly became popular concourse bars.

"We thought people would gather there, but we had no idea they would gather in the numbers they have," Phillies president Dave Montgomery said last week. "Instead of sitting in the upper deck, people are just as happy to come and stand for an entire game. We could not have predicted that."

Nor in 2004 could they have anticipated that most would be young adults, a generation that appeared to have abandoned baseball. Citizens Bank Park, with its boardwalk atmosphere, became a festive fountain of youth, an appealing destination for a new demographic of younger, thirstier

Phillies fans, many of whom don't much care about squeezes and sacrifices.

"The whole group that enjoys hanging out on Ashburn Alley, those people didn't come to the Vet," Montgomery said. "We were dependent on hard-core fans there and families. Now we're benefiting from that 18-to-32 age group."

Except for the drafting of Ryan Howard, Chase Utley, and Jimmy Rollins, there has been no more crucial development in the unprecedented success these Phillies have enjoyed than their $346 million ballpark on Pattison Avenue, a facility its architects now call baseball's "gold standard."

Buttressed by the extra millions of fans and dollars it helped create, the 2009 Phillies won a second consecutive pennant - a feat never achieved in the six other ballparks they had occupied in a 128-year existence. Beginning April 5 in Washington, they will begin their quest for a third.

Philadelphia's baseball paradigm began to shift on April 12, 2004, when, after a dreary final decade at Veterans Stadium, where their fortunes were crumbling like the concrete, the Phillies moved to the new ballpark next door.

Soon, standing-room tickets, unavailable and unnecessary at the Vet, became as sexy as box seats. Young fans came to tailgate, to meet, to eat, to drink, to roam, to mingle, and - oh, yeah - to watch some pretty good baseball.

Since 2000, when a proposed Chinatown locale collapsed and plans for the South Philadelphia stadium took form, the Phils have leaped into the sport's upper echelon, on and off the field. Forbes, which in 1998 ranked the franchise baseball's 23d most valuable, had it at No. 7 in 2009. Between 2000 and 2009, attendance increased by two million, stadium revenue by more than $150 million, and the franchise value by 300-plus percent.

Those figures, astonishing even to the most optimistic Phillies executives, have allowed the payroll to grow from $33 million in 2000 to an estimated $140 million in 2010.

More important, they have allowed the team to sustain its success by locking up contractually a talented, and popular, nucleus, a trick few teams have managed.

"Everything we've been able to do," Montgomery said, "is the result of the stadium and tremendous fan support. We anticipated an uptick [in attendance] when we moved in, but there isn't any way we anticipated drawing 3.6 million."

The Phillies' timing was fortunate. By waiting eight years before jumping onto the retro bandwagon launched by 1992's opening of Baltimore's Camden Yards, they were better able to tailor the ballpark to a vision that was far more fan-focused than when the Vet debuted in 1971.

Its expensive Diamond Club suites, for example, are much closer to the field than suites in Baltimore, Cleveland, or Texas, a post-2000 trend.

Soon the focus was on creating entertainment options and open spaces where fans could gather, including the ballpark's four corner squares, which reference William Penn's city plan.

The most significant open space is Ashburn Alley, the outfield concession and viewing area, where historical displays, proximity to the bullpens, and the smell of cheesesteaks, barbecue, and hoagies lure teeming crowds.

"There was an advantage to coming a number of years after Camden Yards," said Bob McDonnell, one of the architects from the Philadelphia-based firm of Ewing Cole who worked on the project. "We noticed some things there that didn't work. You couldn't see home plate from Eutaw Street," the stadium's outfield concession area. "It was dead out there during games. We wanted Ashburn Alley to be different."

Another of the architects, Craig Schmidt, said the Phillies understood that baseball's constant delays and between-inning breaks could put off younger fans raised in a culture of instant gratification.

"So we tried to incorporate a social or entertainment aspect to the baseball experience, adding places where young people and parents with kids could get up and walk around and still keep track of the game," he said.

Since 2004, six more teams - the New York Yankees and Mets, San Diego Padres, St. Louis Cardinals, Washington Nationals, and, this year, the Minnesota Twins - will have occupied new ballparks, all of them, Montgomery said, having used Citizens Bank Park as a template.

As for the original, Camden Yards, if not for it, the Phillies might today be playing at a remodeled Vet.

After snow-removal efforts caused serious salt damage to its concrete foundation, the Phillies in the late 1980s approached the city about assuming control of a stadium where they were lessees - lessees who got none of the parking revenue, and little of the money generated by concessions and signage.

Overall, their venue revenue was one-fourth of that being generated at new facilities in Baltimore, Denver, and Cleveland. (That all changed at the Bank, where stadium-related revenue reached an estimated $216 million by 2009.) And Philadelphia's shrinking tax base didn't allow for proper maintenance.

Right about then, team president Bill Giles visited Camden Yards.

"Once we saw that," Montgomery said, "we said, 'Uh-uh. We need to change the focus here. We have to look for a new facility.' "

That the Phillies, six years out, are still benefiting from their new ballpark sets them apart from franchises like Detroit, Texas, and Pittsburgh, where the new stadium's financial bounce proved short-lived.

Their experience most closely mirrors Cleveland's. There, the 1994 opening of a downtown stadium, then called Jacobs Field, set off a sustained run of sellouts and meaningful Septembers.

"We were a little different than the Phillies," said John Hart, then the Indians' general manager and now an MLB Network commentator. "We had long been one of the leaders of the have-nots. But when Jacobs Field opened and we became a hot ticket and were able to stretch our payroll, we jumped up near the top of the middle markets.

"We made it our goal to play meaningful games in September, and for nine or 10 years we did that."

While Jacobs Field's bump didn't last forever, neither did Camden Yards'. The Orioles, trapped in a wealthy division, have seen their win totals and attendance plummet.

Fattened coffers, of course, have allowed the Phillies to spend more on scouting and development. Whether that yields replacements as fruitful - and as popular - as this group remains to be seen.

"Fan support is carrying us," Montgomery said. "But at the end of the day, you have to make good decisions to keep going."

As for durability, its architects insist that Citizens Bank Park wasn't designed to be one of those 30-year facilities that marked the last ballpark generation. Already, the Phillies, fearful of Vet-like deterioration, have spent several million dollars to seal the concrete. And Montgomery said a high-definition scoreboard could be next.

"You've got to keep it fresh," Montgomery said, a description that could apply to the roster and the experience as much as the ballpark. "The most important thing is keeping it fresh."