TAMPAFrom the day in 1976 that then-Mayor Bill Poe sold the first wooden plank, the challenge of building Tampa's Riverwalk has been marked by big ambition and a high degree of difficulty.Poe, who died last year at age 82, didn't live to see the vision become reality, but five other mayors did."This is a day that we have waited for, for decades," Mayor Bob Buckhorn said Friday at the opening of the Riverwalk's newest and most high-profile section. Joining him were former Mayors Pam Iorio, Dick Greco, Sandy Freedman and Bob Martinez.The 1,460-foot-long section they cut the ribbon on was expensive ($9.2 million) and hard to build because it had to be set atop pilings sunk into the bed of the Hillsborough River.The new over-the-water promenade goes north from MacDill Park under the Kennedy Boulevard bridge to Curtis Hixon Waterfront Park.It closes a key gap in what is now an unbroken 1.8-mile trail from the Channel District, around the Tampa Convention Center and north to the David A. Straz Jr. Center for the Performing Arts.For shade, the new section has several large fabric awnings stretched over rows of whale-ribbed frames. And the city is applying for a permit to put underwater lights next to the Riverwalk with motion sensors that change the color of the lights as people pass by.But the project took four months longer than planned. And at times, it seemed hexed.Partway into the job, an osprey started to build its nest atop a 150-foot-tall crane. Then the contractor was fined $10,000 after a construction crew got caught on video dumping surplus concrete into the river. Then another crane got snagged on an open span of the Kennedy drawbridge.But residents say the result seems worth the trouble and the wait."I'm excited about it," René Girven, 47, said. "I live in the Element (apartment tower), and I've been watching this project since its inception."In the crowd Friday were a few of the young professionals who Buckhorn hopes to win over by making downtown a place where they want to spend time.It's working, said Savannah Shealy, 25, who lived in San Francisco and Los Angeles before moving to Seminole Heights."It's really cool to see a city like Tampa starting to get a lot of interesting cultural things and places that I can bring my friends and places that I want to come to just to hang out," Shealy said. "I'm a photographer, so anything that's beautiful I'm down for. This meets all those criteria."Also celebrating Friday were U.S. Rep. Kathy Castor, D-Tampa, and U.S. Department of Transportation Under Secretary Peter Rogoff.Castor persuaded Congress to pass a law — "not so easy these days" — changing an 1899 river navigation act so that the project could go forward. The Transportation Department awarded Tampa a $10.9 million federal grant designed to stimulate growth through building transportation projects.The grant also will help pay for the nearby Selmon Greenway trail, plus the next section of the Riverwalk, going north from the Straz Center to Water Works Park. It is expected to be done in April 2016.The grants are "brutally competitive," Rogoff said, with only one application in 16 winning any funding. Even those don't typically get as much as they seek. Tampa's, he said, "rose to the top" because of the vision for the Riverwalk."It's not just a pedestrian facility," he said. "It's an economic development tool, and it's going to keep Tampa growing."Economic spinoffs already are happening, officials say. Among the biggest is Richard Gonzmart's multimillion-dollar restaurant investment in Ulele Native-Inspired Food & Spirits.But they also include smaller ventures, such as Dan and Amanda Fleischbein's new Tampa Bay Water Bike Co., which rents pontoon-mounted water bikes and pedal-powered kayaks at a dock behind the convention center."This is the kind of entrepreneurship that we want to encourage," Buckhorn said.Also encouraged: a laid-back atmosphere. To help set that tone, City Hall recently allowed some bars, hotels and restaurants near the river to start selling drinks that Riverwalk visitors can get to go.Standing in Friday's crowd, Iorio remembered another one.The night in 2004 that the Tampa Bay Lightning won the Stanley Cup, fans spilled out of the arena, only to sort of stand around outside because, she realized, "no one had anyplace to go."With new amenities like Curtis Hixon Waterfront Park and the Riverwalk, that has changed.After walking the entire Riverwalk Friday morning, Iorio said it "has surpassed what we originally thought it would be.""This is fundamentally a different way of looking at Tampa going forward," she said. "Forever more, Tampa will be a city that people will view from the vantage point of the waterfront. And the Riverwalk has made that possible."Contact Richard Danielson at [email protected] or (813) 226-3403. Follow @Danielson_Times.