Oh, and what's even better, when decommissioned, this hidden treasure wasn't dismantled and hauled away.

Perched on a remote ridge in Namadgi National Park is the Orroral Geodetic Observatory, a cylindrical observatory topped by a mine-metre hemispherical dome. Built in 1974, laser pulses were fired from this dome and bounced back via retro-reflector mirrors placed on the moon's surface by Apollo astronauts. The time it took for the lasers to reflect provided information about the motion of the moon, the rotational wobbles of the Earth, continental drift, and even the theory of relativity. Heck, it also housed four atomic clocks which provided Australia with its official time. Amazing!

Improvements in 1981 enabled the observatory to also track man-made satellites, which became its primary function, until tracking ceased in 1998 when facilities were moved to Mount Stromlo.

Unlike the more readily accessible Honeysuckle and nearby Orroral Tracking Stations, which were eventually dismantled, when the dome was decommissioned authorities deemed it far too difficult to remove from its location high on the ridge.

"It's solid nature is what saved it from being demolished, with its massive concrete beams it was easier to board it up than to knock it down," reveals Namadgi National Park manager Brett McNamara.

Instead, park authorities partially encased the dome in besser-blocks where it lay forgotten for almost a quarter of a century, providing little more than an unexpected find for the occasional bushwalker trekking along the western ridge of the Orroral Valley.

However, with the 50th anniversary of the moon landing looming, 18 months ago the staff at Namadgi decided it was time to free the dome from its 25-year time capsule, wipe out the cobwebs and throw its doors open to the public.

"It really is a credit to the staff out here for recognising the significance of the dome as the only piece of tangible evidence left in the park that's linked to space history," explains McNamara. "It was research undertaken in this very dome which led to modern-day GPS technology, something today we take for granted."

However, there's one big catch for any space buffs wanting to visit the dome — you have to walk there, and while the hike starts gently enough in the car park at the former Orroral Tracking Station, before long you'll be huffing and puffing as you ascend a steep old management track. This is the road that workers would have driven to access the dome each day.

In a 1994 article for The Canberra Times, high-country historian Matthew Higgins wrote that while walking up the track he "came across a small diesel tanker (carrying fuel for the complex's generator) which crawled up the hill at little more than walking pace". He continued, "Even if the driver had wanted to stop to give a lift to a walker I doubt whether he could have risking losing his momentum and become unable to resume his painfully slow ascent."

Despite the steep gradient, earlier this week I convinced Mrs Yowie and Sarah, my 11-year-old daughter, to join me on a mission to check out the dome.

It's a hot day, and long closed to vehicles, the only hazards we find on the track are hundreds of skinks of various guises soaking up the midday sun.

As the forest changes from black sallee to candle bark and mountain gum, we stop several times to catch our breath and make-out outlines of faces in the granite boulders which increase in numbers and size, the higher we climb.

In fact, while squabbling with Mrs Yowie whether one rock near the top of the ridge resembles ET or a Dalek, we almost walk past the dome which appears suddenly after one last steep incline.

Sarah races up the stairs to the base of the dome and prises open its heavy metal door. Inside, while the floor is relatively empty, alongside an old electronics panel there is a shelf stocked with information and photos from the dome's heyday.

"I wonder what's up there" asks Sarah peering up through a glass ceiling into the two higher levels. Unfortunately the stairs leading higher up are blocked off, but according to Brett McNamara, "there are plans to open up the mezzanine level in coming years".

"Who knows, one day we could even host special star gazing evenings," says McNamara. "There's some interesting paperwork up there, including an old health and safety report which tells the sorry tale of one poor worker who looked into the laser beam."

Ouch.

While fossicking through some old photos Sarah discovers that, when fired, the laser beam was 'martian' green in colour. "Daddy, that could explain some of the UFO reports in your files," she laughs.

Just behind the dome (make sure you close the door behind you), a short rock scramble leads to a large granite slab perched on the edge of the ridge which provides extensive views down through the Orroral Valley. Wow, I wonder if this is where the dome technicians met for after-work drinks. Although I'm not sure I'd want to face the tortuous drive back down the management track after a beer or two.

Adorning the south-east end of the granite slab is a ball-shaped boulder which is tailor-made for that must-have photo pretending to push it over. Oh, and if you look closely enough at the rock, some (yes, ok, just me) reckon it bears an uncanny resemblance to a giant face. Look for the long nose, crooked mouth and one eyelid closed. Can you see it? Sure you can.

When you eventually leave the dome (allow an hour to explore the dome and surrounds), be sure to follow the recently created loop path which takes you back to the management track via a series of remarkable giant granite tors. Namadgi is known for its granite outcrops, but when God was dishing them out along this ridgeline, (s)he must have been distracted for there are a disproportionately high number here.

Near where the path loops back to the main track, there's one particular boulder, about the size of a double-decker bus, hanging precariously atop two giant support rocks. The track leading under it is like an entry into another world. Indiana Jones eat your heart out. I suspect once instagramers discover this magical place that it will soon earn (and deserve) its own hash tag.

Back down at the car park (take care on the slippery gravel on the way down), leave enough time to snoop around the former Orroral Tracking Station site, currently set amongst autumn splendour from remnant exotic plantings. Also, just beyond the modern toilet block (sorry, still of the composting variety) if you glance over your shoulder and look up high on the ridge you can just make out the top of the white dome reflecting in the sun; quite fitting given the dome's original purpose.

With its rewarding views, dramatic granite tors and tangible link to the pioneering role Canberra scientists have played in space research, it's no overstatement to say this Namadgi walk really is out of this world.

Granite Tors Walk: Although only 8km (allow three hours' walking time, extra for stops) in length, the track is steep in parts with loose, rocky and sandy surfaces. Experienced and fit walkers only. Not recommended for children under 10. The walk begins at the former Orroral Tracking Station site which is located at the end of Orroral Road, about 60km south of Canberra's centre. The Geodetic Observatory (called Lunar Laser Ranger on some old maps) is at the turn-around point of the walk.

Ranger-guided walk: As part of the upcoming 2019 Canberra & Region Heritage Festival (April 13– May 5, and which not surprisingly has a SPACE theme), on Saturday April 27 (10am-2pm), Namadgi ranger Mark 'Elfy' Elford is hosting a free guided walk to the dome. Book early (now) to avoid disappointment. Experienced and fit walkers only. Ph: 6207 2900 or www.act.gov.au/heritagefestival

Did You Know? The entire area of the Granite Tors Walk was burnt in the 2003 bushfires and is still recovering. You can still see blackened trunks, epicormic growth and cracked boulders.

Next week: Namadgi National Park is hosting a smorgasbord of other less strenuous (thankfully), but equally enticing space-themed events during the Canberra & Regional Heritage Festival. I'll reveal my top three in next week's column.

Regular readers may recall this column's exposé on the grave of Henry Dunkley, oddly positioned in the Gunning Sewerage Works (December 5, 2017). To celebrate the upcoming Canberra & Region Heritage Festival, your Akubra-clad columnist has teamed up with a bunch of talented local film makers including Justin Bush, Sebastian Chan and Elliot Ceramidas to tell this real-life tale of treachery and murder for the first time on the small screen.

You can watch the short documentary, The Tragedy of Henry Dunkley, on my YouTube channel from March 23 but if you prefer viewing films the traditional way, the Gunning & District Historical Society is hosting an intimate screening from 5.30pm on the same evening. It's free but there are limited seats. For more info or to book, email: gunninghistory@gmail.com See you there.

Contact Tim: Email: timtheyowieman@bigpond.com or Twitter: @TimYowieor or write c/- The Canberra Times, 9 Pirie St, Fyshwick.

Cryptic Clue: A good place for a Party! Party! Party! Party.

Degree of difficulty: Medium

Last week:

Congratulations to Joan Pratt of Mawson for being the first reader to correctly identify last week's photo as a view from a balloon of the zig-zag path and part of the terraces in the Central Valley at the National Arboretum Canberra.

John Bromhead of Rivett reports the valley "is slowly being populated by trees planted by dignitaries from around the world" and "the zig of the zig-zag is now starting to fill up with gardens being sponsored by individuals and organisations".

The photo attracted a near-record number of correct entries with many recognising the steep landmark from exercise regimes, including Linda Mackay who "runs up it regularly" and Jenny McLeod of Weston who reports it's "a very pleasant walk (or cycle, if it's not busy), as long as you're not in a hurry!"

A number of readers also divulged a close association with the zig-zag, including Geoff Holder of Rivett who admits to "building it" and Robyn Holder who reveals it features in her daughter's range of fitness apparel. Check them out at Zilpah tart Active (www.zilpahtartactive.com.au). Love the towel.

Special note to several readers who entered from afar including Andy Hogan on special assignment in Perth, and Kellie Corbin of Claremont in Tasmania. However the prize for the furthest afield entrant goes to Peter Lambert of Campbell who submitted a very early entry from Beitostølen in Norway while preparing for the Masters Cross Country Skiing World Cup. "If I was to wait until 10am Canberra-time to send the email, I would have to stay up until midnight, but I have a race at 10.25am (Norway time) tomorrow and need my sleep," reported Peter, one of a team of 12 Australian competitors participating in 10-day event. Hopefully next week I'll have news that Lambert's extra sleep paid dividends.

How to enter: Email your guess along with your name and address to timtheyowieman@bigpond.com. The first email sent after 10am, Saturday March 16, 2019 will win a double pass to Dendy - The Home of Quality Cinema.