While a maze of management tracks, historical logging, including firewood lots during World War II, and that tower have somewhat reduced this ''primeval luxuriance'', since becoming a conservation reserve on July 23, 1970, many have lauded Black Mountain as Canberra's very own Central Park - an oasis in the middle of the city.

However, your akubra-clad columnist somewhat disagrees with this bold comparison, for unlike New Yorkers, when it comes to green space Canberrans are spoilt with choice. Within cooee of the city centre we are blessed with an embarrassment of riches of parks and reserves which means we rely less on Black Mountain as a natural refuge than might otherwise be the case.

In the lead-up to Black Mountain Reserve's 50^th anniversary, I've enjoyed daily strolls on over 30km (yes, that many) of walking tracks that criss-cross the 434-hectare reserve. Apart from a couple of early risers puffing up the summit trail, I've only encountered a handful of others exploring the reserve, a far-cry from the parade of headphone-blaring types who traipse-up Mt Ainslie and Red Hill daily.

One group of nature-loving locals who definitely don't take Black Mountain for granted are the Friends of Black Mountain, who, to mark the reserve's big Five O, have published a book that throws the spotlight on the reserve's diverse ecology.

Jointly compiled by naturalist Ian Fraser and plant ecologist Dr Rosemary Purdie, whose dramatic photos highlighting the extent of hail damage to Canberra's trees recently featured in this column (Battered and bruised by hail, March 28), Black Mountain a natural history of a Canberra icon is based on a series of scientific papers prepared by local experts and is richly illustrated with maps and images.

With close reference to this colourful 155-page guide, which is an ideal companion for anyone who wants to discover (or rediscover) this much-loved nature reserve, here are my top five secrets of Black Mountain.

1. Remarkable Rocks: Surrounded by younger volcanic material like Mt Ainslie and Mt Painter, Black Mountain is actually an ''island'' of old sandstone and home to the oldest rocks in Canberra - from the Pittman Formation dating back 460-445 million years. The disused sandstone quarry on the eastern side of Black Mountain which provided stone for several landmark local buildings, including St John Church in Reid (1841), is now a laboratory site for the ANU with no public access.

2. Fantastic Flowers: Given its proximity to the botanic gardens, CSIRO and ANU, it's not surprising that botanists like Dr Purdie have pored over every square metre of the mountain and in doing so have documented 728 (and counting!) species of vascular plants (ferns, conifers and flowering plants ) since 1927. While snooping around the mountain this week, on the Little Black Mountain Loop track I found an amateur naturalist with a macro lens hovered over a spectacular late flowering bright pink Grass triggerplant. I'd walked straight past it. Shows it pays to slow down.

3. Terrific Termites: There are two types of termite mounds found on Black Mountain - a small (up to 50 centimetres in height) rounded mound which is home to Snouted termites and a much taller (up to 2 metres) castle-like fortress mound which are home to Milk termites. There are eight other less conspicuous termite species on the mountain, whose nests are hidden in tree hollows or underground.

4. Mighty Meat ants: Ten different species of termites might sound a lot for an area as small as Black Mountain, but there are also at least 85 species of ants on Black Mountain - that's more than the whole of Great Britain. This includes 13 species of the much maligned meat ant whose ubiquitous low, wide gravel mounds support colonies of thousands of ants. All the ants in the mound are female - the males die after mating.

5. Mysterious Monotremes: If you look closely, many meat ant nests and termite mounds in the reserve are covered in scars and excavations ripped into the tunnels and chambers - tell-tale signs of a hungry echidna's visit. Although these monotremes are often elusive, in the breeding season (usually winter) you might be lucky enough to spot an echidna train which comprises a number of males purposefully following a female in a line.

The book: Black Mountain a natural history of a Canberra icon can be ordered for $25 before August 20, 2020 (afterwards $35) via www.friendsofblackmountain.org.au or 0404 148721.

The walk: This year also marks the 20th Anniversary of the official opening of the Black Mountain Summit Walk, which was a joint project between the ACT Government, Australian National Botanic Gardens, and Telstra. To celebrate, on Saturday July 25 from 9.30am untli 12pm (repeated 1.30pm-4pm) local plant ecologist Michael Doherty is hosting a walk up the north-eastern slopes of Black Mountain to the summit. The walk has some steep sections so is suitable for fit walkers only (including children over the age of 12) and attendance is by gold coin donation. Bookings essential via friendsofblackmountain@gmail.com or 0437 298711.

Did You Know?: The plains surrounding Black Mountain harbour evidence of Aboriginal occupation dating back thousands of years and the mountain itself was both a meeting and ceremonial place. The name Black Mountain first appeared on a map published in Britain in 1834, which included reference to the fieldwork of Robert Dixon and Robert Hoddle who surveyed the area in 1829 and in 1833. According to the ACT Government's Canberra Tracks website, "Hoddle wrote 'Black Hill' under his sketches of both Black Mountain and O'Connor Ridge because both were burnt as part of the local Aboriginals' land management practices. This name stuck for Black Mountain."

It's been one of this column's longest running unsolved mysteries. In Canberra: history of and legends relating to the Federal Capital Territory of the Commonwealth of Australia (1927), journalist and author John Gale reports of a cave "on the eastern side" of Black Mountain, which "was a shelter for several outlaws in the early days". According to Gale, "the cave is the size of an ordinary living room in a modern house" and has "only one means of ingress and egress, and to enter it one has to go on all fours."

Despite several exhaustive searches over the last 20 years, this column has failed to uncover any sign of the cave. Retired geologist Doug Finlayson confirms that while there are currently no caves of such size on Black Mountain, "on vertical creek banks fanglomerate (which forms when rocks shattered by heavy frosts slump down steep slopes and are deposited as alluvial fans) frequently erode to form small caves".

Research undertaken by Dave Wheeler of Tuggeranong, who has also searched in vain for the cave, indicates "it's unlikely to have been a natural cave and was probably made by convicts extending a natural hollowing in the side of a gully".

Doug agrees with Dave's theory. "It is possible that convicts could tunnel into the fanglomerates and make something like a room to live in", he reports. "It wouldn't be too difficult for anyone used to handling a pick and shovel."

Dave's research, outlined in his personal blog 'a Canberra Boy', also concludes "that it's likely the cave was probably located in the area on the mountain which was used as a rubbish dump until 1964". Mmm ... little wonder it can no longer be found.

Clue: Going, going, soon gone?

Degree of difficulty: Medium - Hard

Last week: Congratulations to Linda Meisel of O'Connor who was first to correctly identify the location of last week's photo as a sign on the wall of the building housing the O'Connor post office that used to house a barber shop. Linda just beat Johnny Northside to bragging rights, while Carmel Wroe reports Les De Britt was the last barber on site before it closed about 10 years ago.

How to enter: Email your guess along with your name and suburb to timtheyowieman@bigpond.com. The first email sent after 10am, Saturday July 18, 2020, wins two tickets to Dendy Cinemas.

Mystery solved!

Over many years, several readers have sent in photos of a small circular concrete pad with a hole in the middle, located on the lower eastern slopes of Black Mountain, curious as to its origins. According to Ian Fraser and Rosemary Purdie, authors of Black Mountain: a natural history of a Canberra icon, the man-made oddity is actually the remains of a weatherproof light trap that nearby CSIRO entomologists used to collect insects. Apparently it operated daily until the 1970s, and incredibly, it was still recording new species for Canberra right up to the time the contraption was removed in the 1980s. It is located in bushland just to the west of South Road.