Mark Gwynne took his family to see the White House yesterday, but he didn't get his hopes up. The family physician from North Carolina was expecting to wander into a fortified security zone on Pennsylvania Avenue.

But he found something else entirely. Gone were the concrete planters, temporary fences, Jersey barriers and other obstacles that had lined the two-block stretch of Pennsylvania in front of the White House. In their place was a plaza with granite sidewalks and benches, elegant streetlights and a rustic brown pavement similar to that used at Buckingham Palace in London. Small gray poles served as traffic barriers and guard posts remained, but the security measures no longer dominated.

Gwynne and his family -- his wife, two young children, father and mother -- walked up to the fence and watched Barney, the Bushes' black Scottish terrier, stroll onto the lawn. It was a Washington moment that might have been considered mundane before Sept. 11, 2001.

But in these jittery times of heightened security, Gwynne said, the privilege of having a close look took on new significance. "It's open," said Gwynne, 32. "As an American, this is what I expect. I don't expect to be locked out of our nation's capital."

Gwynne was among the first to visit the new stretch of Pennsylvania Avenue NW. The street between the White House and Lafayette Square was officially reopened to pedestrians about 11 a.m. after a ceremony with first lady Laura Bush. The section of roadway between 15th and 17th streets, one of the most popular tourist destinations in Washington, has been inaccessible to the public since January, when construction of security and aesthetic improvements began.

The pedestrian plaza is one of several security-related construction projects at Washington landmarks. Crews are building an underground visitors' center at the Capitol to provide more amenities to tourists and better security for Congress. Construction is also underway on landscaping and security improvements at the Washington Monument.

John V. Cogbill III, chairman of the National Capital Planning Commission, which initiated the proposal to redesign Pennsylvania Avenue in 2001, said the reopening is a symbolic milestone in a post-Sept. 11 Washington that continues to struggle with striking a balance between security and openness.

"Public spaces can be both secure and welcoming," Cogbill said.

For years, security decisions created a mismatched look outside the White House, with concrete planters and other traffic barriers turning the avenue into what many urban designers and visitors considered an eyesore.

Now, the entrances to Pennsylvania Avenue at 15th and 17th streets are called entry courts and paved with gray granite. The avenue retains its original dimension (84 feet wide), but the surface outside the White House is a most noticeable difference, a grayish-brown pavement made of crushed rock.

Finishing touches remain. Four new guard booths with granite bases and copper roofs await specially designed bulletproof glass, and nearly 90 Princeton American elms will be planted along the avenue in March.

Officials at the Federal Highway Administration, which oversaw the roughly $23 million project, said the renovations were the most significant improvements made to the avenue outside the White House since President Ulysses S. Grant paved it with asphalt in 1876.

"This thoroughfare has always been a connector, connecting the White House and the Capitol and the three branches of government," Bush said. "And a new Pennsylvania Avenue will again connect visitors with this glorious city, with 'the People's House' and with American heritage."

Mayor Anthony A. Williams (D), who joined the first lady at the ceremony, said the reopening to pedestrians was "an important step" to also allowing vehicular traffic there. The street has been closed to traffic since the bombing of the Alfred P. Murrah Federal Building in Oklahoma City in 1995.

Landscape architect Michael Van Valkenburgh designed the guard booths and the gray poles that serve as traffic barriers at 15th and 17th streets NW to be removable if the street were reopened to vehicular traffic, said Elizabeth Miller, project officer for the planning commission.

Staff writer Monte Reel contributed to this report.

A view of the renovated Pennsylvania Avenue, with the White House grounds at right, shows planting areas to be filled with elm trees.