The newest building at the Children's Hospital of Philadelphia will open its doors Monday, providing a state-of-the-art outpatient facility for the body and a roof garden for the soul.

The 12-story Buerger Center for Advanced Pediatric Care, the most expensive building project in Children's history, will cost $425 million, with an additional $175 million needed for equipment. The glass-lined building, streaked with primary colors, sits on Civic Center Boulevard, across the street and just south of the main hospital.

The center is designed to make care more efficient and convenient. A child with a skeletal injury can see an orthopedic surgeon, have X-rays, get casting, and visit the rehab center all on the same floor.

Among other features, the main lobby has a walking ramp with interactive displays that can double as a venue for physical therapy. Likewise, a rock-climbing wall rises on the fourth floor, continuing the designers' guiding principle of "Children in Motion."

The project was financed by a $50 million gift from the family of Alan Buerger, founder of the Coventry life insurance company. The project was also funded through a Kickstarter campaign that raised $94.5 million, a $200 million bond issue, hospital reserves, and other gifts.

In many ways, the jewel of the new building is a 14,000-square-foot roof garden on the sixth floor, the largest of its kind and a first at an outpatient facility, said lead architect Diane Osan of FKP Architects in Houston.

The garden will provide a relatively new kind of care - horticultural therapy - which engages patients in plant-based activities, guided by a trained therapist. It can offer relief from physical and cognitive impairments, reduce stress, and inspire hope.

The garden will be surprisingly local, with a water feature shaped like the Schuylkill and plants laid out to reflect the city's block grid system.

"A child can come and see 12 to 16 different providers in one visit," noted Osan. "There will be inevitable pauses in the care journey where patients have to wait."

Providing diversions for those moments is one goal. Gwenn Fried, the manager of horticultural therapy services at NYU's rehabilitation institute, said that a garden can give patients and families an inspiring way to wait.

The walkways can be used for physical therapy. "For a patient that is relearning to walk, every texture that they encounter [on foot] in an urban environment is a new challenge to them," Osan said.

So the garden has different surfaces for the children to practice on, from concrete steps to those that mimic a city curb, to a running path that cuts through the middle of the garden.

Gary Wangler, who directs the horticultural therapy program at St. Louis Children's Hospital, suggested a less obvious role for gardens. They can help engage and support siblings who feel ignored.

Fried said these outdoor spaces can expose urban kids to nature.

Tending to plants can also encourage children to think that they too can survive and grow, Fried said.

"The kids wonder, 'What will this seed look like in the future?' " she said. "It's very symbolic and connective for them."

She added: "Working outside with nature is normalizing. No one expects to find this in a hospital."