Halala Kanda - known as Firefly Hill to locals in the coastal town of Weligama - was built in 1912 by the son of a wealthy plantation owner, and it went on to host esteemed guests down the years.
But when interior designer Dean Sharpe came across it in 2010, it was a shadow of its former self - its walls collapsed, windows boarded up and its rafters home to bats.
Still, the following year - along with friends Jenny Lewis, Richard Bleasdale and Bentley de Beyer - Dean bought the mansion and two acres of land for $430,000 (£312,761).
He told Insider: "It was a ruin of what it once was. But we walked in and fell in love with it.
"We wanted it to look as authentic as possible, but we didn't want to create a pastiche of what went before."
This appetite for authenticity meant the demolition process, which began in 2012, was time-consuming, as they wanted to keep as much of the original building as possible.
Dean said: "We didn't do a big bonfire and burn everything. Each window frame and roof joist was carefully removed and stacked.
"The demolition took four months to complete.
"The builders were concerned as they needed to get the tarpaulin on the roof to protect it from the monsoon season."
By 2014, they had installed air conditioning, plumbing, and electrical systems, and the mansion was in liveable condition. But there was still more work to do, with a 23m salt water pool installed in the garden and staff quarters built on the hillside.
In doing so, commissioned architect Ross Logie said he believed they'd achieved their objective of modernising the mansion without erasing its history.
He said: "I think we achieved this goal by matching the spirit of the existing villa with harmonious yet contemporary additions.
"For example, the swimming pool and pool pavilion are clearly designed for modern living, yet the pool pavilion shares a fluid style of early-20th-century art nouveau."
Now the friends rent the villa for $1,300 (£945) a night, and while Covid-19 travel restrictions have halted international travel, a tea plantation on the property has helped to cover some of the running costs.
Looking forward, they have plans to make further changes, but the pals are delighted with the transformation.
Dean said: "The Room of Curiosities is my favourite place in the house. I like to sit and read or listen to music and hear the buzz of the house - from the people in the pool, to the clatter in the kitchen.
"There have been lots of wonderful little moments."
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