On a Saturday morning last November, programme manager Dilpreet Kaur swopped her fashionable heels for sturdy trekking boots.
With 30 other people, the 29-yearold trudged through the dense forest along Old Upper Thomson Road to visit the remnants of an old Hainanese village that has been abandoned since the 1970s.
They came across a large water receptacle shrouded by green tendrils, weathered brick structures and random items such as a radio and baby doll peeking out from the forest floor.
"It is a place I would never have discovered or visited by myself," Ms Kaur says.
The city slicker had signed up for a free urban exploring trek with Temasek Rural Exploring Enthusiasts, or T.R.E.E.
She is part of a growing number of Singaporeans who have developed an interest in urban exploration, where they traverse the island in search of hidden or little-known places where ruins still stand.
There are a handful of urban explorer groups in Singapore, including Urban Explorers of Singapore, but T.R.E.E. is perhaps the only one that regularly organises free guided treks for the public.
Started in 2014, the group has 11 members in their late 20s to 50s who are in societies that focus on photography, nature and heritage .
In 2015, the group began to open its exploration trails to friends, before extending these to the public in the second half of last year.
Mr Muhammad Herizzad Ruslan, its team leader, says: "We hope to show unseen sides of Singapore that might disappear one day as the country continues to develop."
Treks are organised at least twice a month and participant numbers have risen from 30 when it started to about 50, says assistant team leader Faye Joseph S. Ramos, 36.
They have visited the ruins of Syonan Jinja at MacRitchie Reservoir, a Shinto shrine built by the Japanese army during the Occupation, and crossed the Causeway to Johor Baru to visit a forgotten artillery battery set up as part of Singapore's defences during World War II.
The group had discovered these places during random wanders, by word of mouth or when they were younger. Its next trek on Sunday morningwill check out the former Bukit Timah Railway Station - a place Mr Muhammad Herizzad, 34, remembers from his childhood.
"I remember the station was where the rail tracks were switched. It was one of the smaller stations," he recalls.
Participants will get to peek into its control office and walk along the rail corridor towards Bukit Timah Nature Reserve to check out the caves there.
Safety is important when it comes to organising these treks for the public. Before each trek, the team would recce the site at least thrice to ensure it is safe to explore.
The information on each location is mostly sourced from old texts, photos and trusted sources who had lived or worked in the area, says Mr Muhammad Herizzad.
A key concern is whether public access is allowed.
Mr Ramos says: "For places that have a 'no trespassing' sign, we will request permission from the relevant authority to enter. If not, we will not go there."
To cope with more participants, they divide the group and do regular headcounts. Events are posted on the group's Facebook page and a disclaimer is included on how arduous each trek might be.
A regular participant is 46-yearold housewife Louise Raggett. Besides learning about Singapore and its history, she particularly likes the anecdotes that the team shares. "The stories are not what you read on the Web," she says.