At ground level, leaves of the giant rubber tree at Construction House in Hobart's CBD press against the glass, visible to passers by.
What they can't see is the plant grows up through the entire seven-storey stairwell.
Steven Holdway has been an arborist for three decades and looks after the 20-metre plant.
"This unique tree would be the largest indoor plant I've ever seen anywhere I've been in Tassie or Australia," he said.
Mr Holdway visits the building, now owned by the Master Builders Association of Tasmania, "every four to six months" to manage the tree.
Even though it towers seven storeys high, Mr Holdway describes it as an "urban bonsai" because, "it can only get so big because there's only so much room".
This rubber plant, ficus elastica, is native to South-East Asia.
In the wild, the species can grow up to 40-metres high.
Who knows how tall this one would get if it didn't have the concrete ceiling on the top floor to contend with?
Who exactly planted the tree and why is unknown but the "generosity" of the staircase's design plays a huge role in the fact it grew so large.
The building, finished in 1959, is a perfect example of "new construction techniques allowing some really generous moments in that building", according to Hobart-based architect Genevieve Lilley.
The rockery at the base of the stairs, from which the rubber tree grows, was a common design feature of the post-war period, with office spaces often including greenery and fish ponds, she said.
One notable local has a particular interest in the rubber tree's origins.
"I just wonder who planted that seed? If we all planted a seed like that the planet would be in a better position," former Greens leader Bob Brown said.
The Bob Brown Foundation has leased offices on the fourth floor for the past seven years.
Its namesake loves having the tree just metres away.
"Everyone that comes into this building, from the ground floor all the way to the top, engages with this plant," Dr Brown said.
The large plant helps provide oxygen to the building's occupants, and it has another important role.
"I've met local business owners and people who work in the city that know the plant quite uniquely and intimately and observe it often," Mr Holdway said.
That sentiment is echoed by Dr Brown, who practised medicine before entering politics.
"It does make you feel easy; greenery always does that," he said.
Dr Brown believes the indoor tree may be a world-record breaker.
"I looked up Google and sure enough the Americans have got the world's tallest indoor plant and it's 20-feet high.
Tasmania has thrown the gauntlet down — find a bigger indoor plant anywhere else.
Until then, we're claiming top spot.
