Beyond the door it's black as ink. Burkevics switches on his torch, its beam bounces off his high-vis vest, reflecting into a dark void. Onwards we venture. Old airconditioning ducts are haphazardly strewn across the floor and I almost trip over the rusting remains of an old bike with only one wheel. It's like entering a Doctor Who props cupboard from the 1970s.

We eventually reach a wobbly old security roller door, which Burkevics asks me to help him lift. As we scurry beneath it and let it go behind us, the metal frame crashes into the concrete floor sending a puff of dust into the stale air.

Oh dear, what am I getting myself into?

Ahead, our torches light up a small room, complete with a spider web-covered security grille. At first glance you'd be excused for thinking it's a secret subterranean prison cell, but closer inspection reveals a desk and rickety swivel chair with a torn seat inside the room. A door to the side is emblazoned with the words "attendant".

"This was the epicentre of this little-known public space which has been closed for over 25 years," Burkevics says. "Back in 1972 the Woden bus interchange was originally intended as a transit centre, so they built this special shower block where interstate passengers could pay for a shower, to freshen themselves up before continuing on their journey.

"For the grand sum of 50¢, one could have a shower, be supplied with soap and a towel and purchase single-use shampoo and conditioner for 5¢ cents from the attendant who sat right here," says Burkevics, who is on a quest to uncover as much history of this public facility before it is bulldozed in coming weeks as part of the ACT government's $3.15 million redevelopment of the much-maligned bus station.

Burkevics' detective work has already revealed that just prior to their closure in 1992, the showers and toilets were run by an elderly man and his wife. "I am sure that the man was effectively the owner of the position and his wife helped him so he could keep his job," Burkevics says.

It also turns out that it wasn't only travellers who used the showers. According to Burkevics' research, "as buses weren't airconditioned back then, many of the drivers would avail themselves of the facilities to have a shower a change a shirt and freshen up during the day".

Since the closure of the showers, it's been used as an ACTION storeroom and hidden in various nooks and crannies are broken poles, old timetables and lost property.

The walls are adorned with graffiti, like a "spaced-out" written over the top of a classic saucer-shaped UFO. Was it scrawled on the wall during the heyday of the space race of the early 1970s? Or was it the handiwork of urban explorers (an expanding network of adventurous daredevils who illegally explore drains and other hidden places beneath our cities) who may have broken into this space in more recent years? We may never know.

This column's passion for a good bush mystery is well documented, however, our urban environment, even in a city as young as ours, can also hold secrets. Sure, for some this may just be another musty old public amenities block, but Burkevics believes this long-lost part in our public transport network has a story to tell about our city. "I understand many of the customers had come from interstate and showered here before their job interviews with the expanding public service in the 1970s and 1980s," says Burkevics, who'd love to hear more of their stories before the imminent roar of the bulldozers.

Did you know?: The "snake pit" was a nickname given by locals to the western end of the Woden bus interchange as it has traditionally been a place where itinerant youths have gathered, has poor lighting and is generally avoided by the general public after dark.

The door leading into the long-forgotten subterranean world at the Woden bus interchange isn't Canberra's only secret green door. Arguably our city's most famous green door is on the ground level of East Block in Queen Victoria Terrace, Parkes. The building is now home to the National Archives of Australia, but during the 1950s housed the Australian Security Intelligence Organisation (ASIO), Australia's spy agency.

"Back in the late 1950s East Block was occupied by the prime minister's department and under it came both ASIO and the Commonwealth Audit Office where I was employed," recalls Kevin Mulcahy, who worked in an office overlooking the door.

"We used to see guys coming and going through that door but we didn't know much about it other than it was ASIO's head office," Mulcahy says.

Apparently at the end of the day, in typical "spy" fashion, small groups of ASIO officers would exit the door and then walk off in different directions, only to "reappear" 10 minutes later at the Wellington Hotel (since demolished) on the corner of National Capital Circuit and Canberra Avenue for a drink.

If you've got a story about the green door, I'd love to hear from you.

Our region's labyrinth-creating craze continues unabated. During the week, one of my attentive Yass correspondents spotted the outline of a labyrinth traced in flour on a local oval. On further investigation, it turned out to be a rehearsal for a more permanent labyrinth which will be painted onto the top of a tank at Cooma Cottage in time for today's launch of Sculpture in the Paddock, the rural town's annual outdoor art fest which runs until October 15.

Earlier this year, many readers expressed their surprise at the role Jerrabomberra Wetlands played in our wartime history, being the location of the Duntroon World War I instructional trench system (Digging up the Past, January 31). There is a celebration this week to mark the 25th anniversary of the current incarnation of the area as a nature reserve.

What: A sunset supper and a presentation by historian Mark Butz in which he will explore the various perspectives of the Jerrabomberra Wetlands and the Jerrabomberra/Molonglo floodplain in Canberra's landscape and history.
When? 6pm-8pm, Thursday September 24.
Where: Jerrabomberra Wetlands Centre, 2 Dairy Road, Fyshwick.
Expect: To marvel at the wetlands' broader values which derive not only from its wartime role, but also its geomorphology, Aboriginal history and colonial past, much of which Butz has only recently rediscovered.
Cost: Free, but you need to RSVP to: lori.gould@woodlandsandwetlands.org.au or Ph: 0439 030058.
Contact Tim: Email: timtheyowieman@bigpond.com or Twitter: @TimYowie or write c/- The Canberra Times, 9 Pirie St, Fyshwick. You can see a selection of past columns at: canberratimes.com.au/act-news/by/tim-the-yowie-man

Clue: Often full of cakes, not animals.
Degree of difficulty: Medium.

Last week: Congratulations to 16-year-old Gavin Hillier, of Kaleen, who was first to correctly identify last week's photo, sent in by Glen Howard, of Giralang, as the gantry for the new bridge over the Molonglo River, part of the Monaro Highway/ Majura Parkway upgrade near the existing intersection on Pialligo Avenue. The triumphant teenager just beat Athol Morris, of Forde, and Will Orgill, of Jerrabomberra, to the coveted prize.
How to enter: Email your guess along with your name and address to timtheyowieman@bigpond.com. The first email sent after 10am, Saturday, September 19, 2015, with the correct answer wins a double pass to Dendy cinemas.