Ground-level first impressions — the all-important pedestrian approach — mean everything, even at the most soaring architectural monuments.

A visit to the Eiffel Tower, for example, wouldn't be the same without passing through the Champ de Mars, a sprawling public greenspace once used as a military parade ground.

The Washington Monument would stick out like a particularly lengthy soar thumb if it weren't for the surrounding grassy expanses of the National Mall.

For the past 50 years, the pedestrian approach to the Gateway Arch in St. Louis — and no disrespect to original landscape architect, the late, great Dan Kiley — has been downright terrible.

For such an iconic structure, the 630-foot-tall catenary arch has long stood in what CityLab calls "splendid isolation" — a lonely island severed from downtown St. Louis by a pedestrian-deterring tangle of freeways, surface roads and parking structures.

Considered an anchor of the city's Mississippi riverfront, there's really not much for the Gateway Arch to anchor. Disconnected from the urban landscape, Eero Saarinen's steel monolith, until now, has largely existed in a void. A pretty void — Kiley's pond-flanked, neatly geometric park has its midcentury charms — but a void nonetheless. As Zach Mortice writes for CityLab, this "car-chocked hub of tourist activity" is "good for driving to, parking, snapping a few photos, and driving out again." Curious that a structure so emblematic of St. Louis has so little to do with the city itself.

About $380 million later, the Gateway Arch is at long last fused with downtown St. Louis as part of a five-years-in-the-making revamp of the site — an expansive facelift that's yielded both a world-class new museum buried at the feet of the arch and upgraded national park status. Previously known as the Jefferson National Expansion Memorial, the overhauled grounds have been rechristened Gateway Arch National Park.

While both these things — the just-opened underground museum and the new national park designation — are garnering a bulk of the fanfare, it's the landscaping enhancements that are the most transformative aspect of the rejuvenated site. After over 50 years spent defining the city of St. Louis, the Gateway Arch is now part of it.

A freeway-topping link to downtown

Freeway-capping park projects — or "lid parks" — are nothing new.

Seattle broke new ground when it blanketed Intestate 5 with visionary landscape architect Lawrence Halprin's aptly named Freeway Park in 1976. In the years that followed, other cities — Dallas, Boston and Duluth, Minnesota, among them — have reconnected severed neighborhoods by topping highways with public greenspaces. Even Atlanta, a sprawling city with a mess of freeways running through its heart, is looking to "re-stitch" two major business districts by placing a greenery-laden deck park over the Downtown Connector (I-75/85).

Gateway Arch National Park, St. Louis The freeway-topping 'land bridge' at Gateway Arch National Park begins to take form. (Photo: xiquinhosilva/flickr)

The slice of parkland that now spans over I-44 (née I-70) to connect the Gateway Arch with downtown St. Louis is decidedly more modest in scale but no less dramatic.

Writes the Chicago Tribune's Blair Kamin of the freeway-topping "broad land bridge:"

In contrast to the old highway bridges that led to the Arch, for example, the new land bridge uses acoustical walls and plantings to keep the interstate out of sight and muffle the sound of cars and trucks. It succeeds so well that many visitors will not be aware that they're walking across a bridge.

The space — Washington Post architecture critic Philip Kennicott calls it a "parklike pedestrian platform" — creates an uninterrupted urban greenway that extends from the riverside to the Old St. Louis County Courthouse, a St. Louis architectural icon that many visitors to the Gateway Arch may have previously neglected to visit.

And who could blame them?

The roaring sunken freeway separating the two landmarks certainly doesn't make traveling by foot between the two spots the most pleasant of experiences, particularly for those with disabilities. (Built in 1828, the Old Courthouse has been a part of the Jefferson National Expansion Memorial since 1935. Up until 1965 when the Gateway Arch was completed, it was its centerpiece. Like the arch, the old courthouse is now part of the 91-acre Gateway Arch National Park. On the opposite side of the courthouse is Kiener Plaza Park, a popular public greenspace that's also been substantially revamped.)

As the Tribune writes, the driving vision of Michael Van Valkenburgh, the Brooklyn-based landscape architect (Brooklyn Bridge Park, Pittsburgh's Allegheny Riverfront Park) tasked with revamping the grounds around the arch, was to "undo the islandlike quality of the park."

"There was an inhospitableness about the whole place before that we were trying to make more humane and make a better visitor experience," says Van Valkenburgh.

Better views, improved accessibility

In addition to the 97-foot-wide, 274-feet-long park-cum-freeway lid, which was completed in 2014 and then topped with over 200 trees and 15,000 cubic yards of soil before opening to the public in March of this year, a grass amphitheater has replaced a view-blocking eyesore of a parking structure to the north of the arch next to the Eads Bridge, a steel-truss wonder of late 19th century engineering. Like the lid park, the amphitheater and an additional 8 acres of new parkland provide a seamless connection to downtown St. Louis, specifically the historic Laclede's Landing district.

What's more, the Tribune notes that accessibility-improving ramps leading from the arch grounds down to the Mississippi riverfront have been added as part of the overhaul "providing people with disabilities a beautiful alternative, lined with swaths of blue lyme grass, to a monumental flight of stairs." To replace the grounds' vulnerable ash trees, a small army of London plane trees have also been planted along the park's pathways —5.4 miles of new footpaths have been added — to provide additional shade and give park-goers a place to seek relief in the sweltering summertime heat. (The trees that are planted atop I-44 are small-ish varieties, including red buds, magnolias and buckeyes.)

"This is the fastest-growing area of the region," Eric Moraczewski, executive director of the nonprofit Gateway Arch Park Foundation, tells the Tribune. He notes that spiffing up the park while providing a pedestrian link between downtown and the riverfront "is a catalyst for driving people down here. They want that green space."

Pursuing economic revitalization with revamped urban parkland

With its sleek new museum and riverfront-revitalizing landscaping overhaul complete, will Gateway Arch National Park — bigger, greener and more accessible than what came before it — be able to kick local economic growth into high gear like Moraczewski hopes it will? Will St. Louis residents flock to their city's newly minted urban national park?

St. Louis, a markedly divided city, is counting on it.

As the Chicago Tribune notes, the ambitious redevelopment project, financed jointly by private donors and taxpayers, is expected to attract record crowds to the arch. With annual attendance normally in the ballpark of 2.5 million, it's expected to swell to 3.25 million now that the new museum, which boasts entrances that stretch even closer to downtown than before, is open. (Attendance dropped to historic lows during the multiyear makeover.)

Across I-44 adjacent to the park's western section, new hotels are being built, covetable commercial space is being leased and historic buildings are being transformed into residential properties. Trendy new restaurants, shops and other amenities are also popping up in the area after an extended period of decline.

Just south of the arch on the riverfront, developers are mulling the total transformation of Chouteau's Landing, a down-and-out industrial area long obscured by bridges, highways and train tracks.

Also downtown, not too far from Gateway Arch National Park, there's a $45 million new aquarium under construction at historic St. Louis Union Station. It's due to open in fall 2019.

"The fact that this is all fluid now, that it's a park that just kind of unfolds into the downtown, is going to give us a lot of opportunity to attract people that otherwise wouldn't have come," said Missy Kelley, president and CEO of Downtown STL Inc, tells the St. Louis Post-Dispatch. "Once people are down here, they come for one reason, then they see all the other assets that downtown St. Louis has to offer, not to mention beautiful buildings to look at and beautiful buildings to eat at or shop in. I think there's a wonderful opportunity for our downtown economy to take a very positive turn because of this."

Fair St. Louis, a free event dubbed as "America's Biggest Birthday Party," kicked off on the Fourth of July and could serve as an unofficial barometer as to how the public will react to the park's $380 million upgrade. Traditionally held on the arch grounds, the three-day festival has relocated to Forest Park, fabled former site of the 1904 St. Louis World's Fair, over the past four summers due to ongoing construction and landscaping at the arch.

While the festival has yet to conclude at the time of the writing of this article, there's no argument that the timing of the fair and the official opening of Gateway Arch National Park are nothing but advantageous.

As Kelley tells the Post-Dispatch: "It's like the best open house you can possibly have for the Arch grounds."

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.