Massimo, Giovanni and Gilberto are not your ordinary gardeners.
The three Italians are expert climbers and arboriculturists, merging their deep passion for vegetation with a serious head for heights.
Once every three months, they abseil from the roof of Milan's 110-metre vertical forest - a death-defying stunt which has earned them the nickname ‘the flying gardeners’.
Floor by floor, they trim, prune and water the 21,000 trees, shrubs and perennials which call the building home.
What exactly is Bosco Verticale?
The pair of residential towers were designed by 65-year-old Italian architect Stefano Boeri, for whom plant life is more than a simple aesthetic consideration.
“I try to promote urban forestation because that's what we need," says the Milanese urban planner, citing the environmental benefits of incorporating nature into architectural projects of this kind.
"We have to multiply the number of trees everywhere. And the reasons are very clear. It’s a faster, cheaper and more inclusive way to try to take down global warming.”
The building’s vegetation converts an average of 19,958 kilograms of carbon each year, while mitigating noise pollution from the street-level traffic below.
The high-rises are also entirely self-sufficient, using renewable energy from solar panels and filtered waste water to sustain the buildings' plant life.
Taking gardening to new heights
With over 60 varieties of trees and 94 varieties of plant, tending to Bosco Verticale’s vegetation is not for the faint hearted.
The trees that adorn the two towers are mainly deciduous, meaning their external appearance alters throughout the year.
Maintaining this foliage ensures Bosco Verticale remains habitable for humans and wildlife alike.
On top of the building's 300 occupants, there is now a growing population of birdlife too.
“Trees were the first tenants and moved here ten years ago,” adds Boeri, "but it has also started to host 20 different species of birds.”
Each apartment contains a balcony with a number of medium-sized trees, shrubs and climbing plants.
In total, the foliage provides shelter and sustenance for an estimated 1,600 birds and butterflies.
Watch the video above to see the flying gardeners at work.