Phase Two of Miami’s long-awaited Underline trail is ready to go. Here’s what to know.

It’s still several days until the opening of the long-promised second phase of The Underline, the $140 million urban trail and linear park that runs under the elevated Metrorail tracks. But already the joggers, cyclists, scooter-riders, skaters and dog-walkers — not to mention the monarch butterflies — are out basking in the verdant transformation of more than two miles of once-scruffy terrain.

The trail section — 2.14 miles long, to be precise — formally opens with a ribbon-cutting on Wednesday. But it’s been a long wait, and the construction fences and barriers are finally down, so eager neighbors, Metrorail riders and people on all sorts of non-motorized conveyances have begun exploring the new stretch of trail even as crews apply some final touches.

“People are already making it their own,” said Meg Daly, founder and president of Friends of The Underline, the non-profit group that launched and manages the trail, which is being built by Miami-Dade County. “We’ll be out doing our checks, and they’ll say ‘thank you’ as they go by. It’s very organic and it’s very gratifying. There’s a lot of people excited about what’s coming.”

The new Underline segment connects to the first completed half-mile phase in Brickell, which starts at the Miami River and opened in 2021, at Southwest 13th Street. Phase Two then runs continuously south through Brickell, The Roads and the Vizcaya Metrorail Station to Silver Bluff, ending at Southwest 19th Avenue.

In contrast to the intensely urban Brickell Backyard section, which is centered around the frenetically bustling Brickell Metrorail station and sits in the middle of a dense forest of high-rises, Phase Two is a veritable forest of green: Thousands of new native trees and plants envelop, cool and help shade the trail as it wends its way south from Brickell and along traffic-clogged U.S. 1 through a series of low-scale residential neighborhoods.

As they grow in, the new plantings — which supplement a scrim of long-standing trees and palms along the route — will provide a buffer for users from the noxious automobile traffic on the highway, Daly said. Milkweed planted along The Roads neighborhood has already begun attracting monarchs, she noted.

“You just feel insulated in nature,” she said.

The second-phase inauguration, delayed by months by weather issues and a simultaneous FPL project to bury high-tension power lines along the Metrorail route, comes as construction has already started on The Underline’s third and final section.

The last seven-mile stretch, the longest and most complex of the three phases, will run through Coconut Grove, Coral Gables and South Miami to the Dadeland South station to complete the 10-mile trail. That will come sometime in late 2025 or early 2026, depending to a large degree on progress on the FPL project, said Irene Hegedus, Underline project manager for the county department of transportation and public works.

Wednesday’s ribbon-cutting is by invitation only, but the first public event to mark the Phase Two opening will come on May 4 — with a community block party with food and activities at the Underline’s expansive new Hammock Playground, which sits astride the city’s Simpson Park along Southwest First Avenue at 15th Road.

The playground, Daly said, was inspired by the preserved hardwood hammock at Simpson Park and blends nature, art and play. Nature-inspired play equipment has been interspersed with playful, unconventional Modified Social Benches by Danish artist Jeppe Hein, which have become popular fixtures in parks around the world.

The new section boasts two other features for gatherings and relaxation:

* A new plaza at Vizcaya Station features shaded seating. A labyrinth inscribed in the pavement recalls those at the nearby Vizcaya Museum and Gardens and will serve as a serene setting for guided meditation sessions and community markets, Daly said.

* The Rain Garden, at Southwest 17th Avenue near the popular El Carajo gas-station Spanish restaurant, is the first of a series of planned bioswales along the Underline. These are landscaped depressions designed to collect and filter rainwater and runoff in spots along the route that tend to flood. The Rain Garden has a curving limestone bench for contemplation.

Like the Brickell section, The Underline’s new phase will have lighting after dark and rest stops with water fountains.

The new section for the first time displays the full scope of The Underline’s intent: A lushly landscaped, continuous running, walking and cycling trail that provides an alluring new way to connect Metrorail stations and the densely populated neighborhoods that run along it.

Once the route of the rail line built by industrialist and Miami co-founder Henry Flagler, the land below the Metrorail guideway was for decades treated mostly as leftover space. An unlit, bare-bones paved pathway ran through it, but was lightly used though it sat for decades in plain sight of thousands of daily commuters. Daly, inspired by the success of New York’s High Line, pushed an unlikely vision for the transformation of acres and acres of sorely underused public space.

An easy ride through the new segment can furnish a clear sense of the metamorphosis, as well as the compromises made necessary by the irregular width of the available space.

One thing that is immediately clear: Even before it’s fully grown in, the vegetation provides a soothing feeling of enclosure and a surprisingly effective screening off of the traffic and noise of U.S. 1.

The safety of once-perilous street intersections has been significantly improved through various means, including brighter and far more visible striping for the bike and pedestrian paths, no-right-run-on-red signs for motorists coming to the highway from side streets, and flashing beacons at crossings at Southwest 25th and 26th Roads that carry traffic to and from Interstate 95.

Designers and builders for Phase Two, a local team made up of Lead Engineering Contractors and landscape architect Ken Gardner of GSLA Design, sought whenever possible to install wide, separate pathways for people on foot and people on bikes and other wheeled devices. The pavement is uniformly smooth and comfortable, and sight lines are significantly clearer compared to the old M-Path, which wound around columns that obstructed views of the pathway.

But some narrow stretches required shared pavement and, potentially, a tight squeeze at busy times.

South of the new playground, for instance, the Underline narrows as the Metrorail comes down to ground level along The Roads. It widens again as the line becomes elevated just before the Vizcaya station, then narrows again along the station property. Once past the station, however, an expansive right of way means separated and comfortable, broad paths for users.

Those for faster-moving cyclists are straight, for safety, and placed closer to U.S. 1. The pedestrian paths wind around more and sit across a wide, landscaped area from the bike path.

The behavior of some of the segment’s early users, though, also raise some potential issues if The Underline, as its sponsors fervently hope, becomes heavily traveled.

The Brickell segment, though it provides some separation of paths when possible, illustrates the dilemma amid at times heavy foot traffic: People ignore markings and walk on the bike paths, obstructing cyclists and sometimes drawing annoyed warning shouts. Daly acknowledges the conflicts may be inevitable given that location, but most people navigate them reasonably well.

But the new section, like the rest of the Underline, is meant to allow people on bikes and other wheeled vehicles to move relatively quickly, in part to encourage commuting and travel between Metro stations.

Some wrong-way users were in evidence on a recent late afternoon: One gas-powered motor scooter on the trail. People strolling in the bike paths and not heeding called-out warnings. Dog walkers with unleashed pets, and others with long, extendable leashes or multiple dogs effectively taking up the entire width of shared pathways. A woman in an SUV parked in the Underline swale at a crosswalk on Southwest First Avenue while she talked on her cellphone.

But Daly notes the trail will be patrolled 24 hours a day by private security officers on e-bikes who will educate users and enforce separation and other safety rules. That includes no gas-powered motor scooters and dogs on leashes at all times.

She is confident that as traffic on The Underline grows, the ultimate measure of success for the project, so will knowledge of proper use and behavior.

“I think some of that will come tough education, and I think it’s also going to come from some enforcement,” Daly said. “You are going to have a lot more people using it. And when there are more, there will be more recognition of the rules. There will be a lot of compliance.”