Not since that landmark wooden structure on the side of the M31 near Campbelltown first appeared in this column (it turned out to be a water tank stand, not a treehouse) almost 10 years ago have so many theories been put forward by readers to explain the origins an object.

While some theories to explain the over-sized concrete block located in parkland on Suttor Street in Ainslie appear to have been well thought through, others are more fanciful, to say the least.

A number of readers suggested, I hope tongue-in-cheek, that it is an over-sized coffin of sorts. "It definitely looks like a tomb," claims George C of Boorowa. Jeff Smith thinks it might even lead to "a secret tunnel". "I bet if you lift it up there'll be a trap door underneath it, maybe even with Harold Holt's skeleton," he quips.

Among the more plausible theories are that the block provided a tie-down point for light aircraft based at Canberra's first aerodrome which in the mid-1920s was centred on nearby Dickson.

Still on the aeronautical theme, Chanelle Fyve suggests it could be an old tie-down point for hot air balloons. Thomas James goes one step further. "It's a tether for Skywhale," he muses.

Kevin Mulcahy of Tura Beach but who spent most of his life in Canberra recalls "blocks of similar appearance complete with three guy-wires and a mast were once used as a makeshift tower by firefighters to dry their wet hoses at a nearby fire station". "Maybe it's just another of those," he speculates. If it did once support a mast, Lesa Coleman believes it may have been for an historic transmitter aerial.

However, the majority of readers went down a rabbit warren of theories relating to drains. "Could it be an access point for storm water run-off?" asks David Parisi. "Maybe it's an access point to an underground storm water tank for managing peak water flows," suggests Graeme Freedman, while Kurt Sedlmaier reckons "it looks like an old grease trap".

Many readers also commented on the block's distinctive metal hook. "It was common years ago for lifting lugs to be formed into concrete this way before we had to worry about engineering and safe lifting loads," reports Neil Clarke. Andre Sphensis postulates the lug was for a different purpose. "Perhaps it was a pedestal for a now departed statue, attached by the loop of iron?"

Some readers even speculated it was remnant infrastructure from a long lost playground. "First thing that came to mind was a playground implement anchor for a seesaw or roundabout," writes Glenn Lyons.

Several readers also echoed the pleas of Alex Reischl. "Ask the local council to open it, and do a big reveal," she begs.

Thankfully, there's no need to ask for the concrete box to be prised open or examined more closely for 85-year-old Kenneth (Ken) Sharp, who has lived in Ainslie since 1939, has solved the mystery.

Unfortunately for Jeff Smith and other exponents of his outlandish theory, we aren't going to find Harold Holt's skeleton beneath it, for it turns out the heavy concrete block was used as a counter-weight for a tractor-come-digger. Nothing more, nothing less.

"Patrick (Paddy) Kinane lived opposite the park and used to use his machine to dig holes and plough fields in the region but when he chucked in his job he dumped it here and it's stayed here ever since," explains Ken.

"Luckily Paddy dumped it in a location which didn't interfere with us using the parkland for games of cricket and football," recalls Ken, who until having to move four years ago due to having Mr Fluffy in his home, lived right opposite the unofficial park.

In the late 1940s, with the help of neighbours, Ken "cut a strip into the paddock and had a real cricket wicket".

"It definitely favoured the batsmen for the bowler always had to run uphill," he laughs.

Ken's son Robert remembers the chunk of concrete from his own childhood. "When I was growing up here in the late 1970s and early 1980s, it was under a big tree which has since gone," he recalls. "It really was a great spot to sit and have a rest or to watch others play."

Reminiscing about the concrete block triggered a flood of memories for Ken who reckons "Canberra has changed for the worse", especially in recent decades. "There's way too much urban infill," he argues. "When I grew up there was no fruit or veggie markets, we had to grow all our own in our backyard."

Ken especially remember the war years. "We had coupons for butter, sugar and tea, and regularly had air raid drills where we would have to shelter in a trench at the old Ainslie School," he recalls.

Given the interest in the concrete block, your akubra-clad columnist suggested that a little sign be placed near the block explaining its origins, but Ken wasn't keen on the idea.

"Then people might think it's of monetary value and vandalise or steal it," he says. Indeed.

Still in Ainslie, several new readers have asked about the historic bus stop located near the corner of Cowper and Cox streets which "appears to have a room with no windows, doors or other signs of entry or exit, tacked onto it".

Regular readers may recall that this column once published original plans for the 'secret room' which confirmed its purpose as a driver's rest room, used when the Ainslie bus stop was a terminus of the bus service.

This week marks the 200th anniversary of when governor Lachlan Macquarie 'raised a bumper' while on a hilltop overlooking a 'noble expanse of water' and re-named Weereewa (often spelled Weereewaa and sometimes referred to as Ngungara) after the reigning monarch of the time, King George IV.

While Patrick De Deckker, emeritus professor at the ANU's College of Science, has joined this column's call for the lake to revert to its original, much more meaningful name(s), he also argues that the enigmatic lake be heritage listed.

At a lecture earlier this week in Goulburn, Patrick outlined the main reasons why he believes the lake should be given national heritage status.

1. Commencing with the NSW Government Astronomer and first Australian Meteorologist H.G. Russell who obtained a record of lake level changes going back to 1820, Lake George is one of only three sites in the world that provides important data on environmental change that precedes the instrumental record. In addition, sediments obtained from below the lake floor extend the record of environmental change going back over 3.5 million years. It tells of vegetation change, fire history and climatic shifts.

2. There is an important record of human interaction with the landscape that is now well documented for the last 200 years, and people before that also visited the Lake George area as evidenced by archaeological artefacts found in the vicinity of the lake.

3. A large range of scientists including biologists, meteorologists, water scientists, geologists, palaeoecologists and palynologists have investigated other aspects of the lake over many decades. Well over 60 publications are available detailing various aspects of science conducted/observed on the lake.

4. The lake has been a fascination and focus for many artists, such as poets, painters, musicians, photographers and ballet dancers, many of whom participated in exhibitions and festivals celebrating the lake.

Other sites on the National Heritage List, which documents the places of outstanding heritage importance to Australia, include the Australian Alps National Park and Bondi Beach. Heck, if Bondi Beach is on the list, surely Lake George has a worthy claim.

Clue: Near the banks of the 'bidgee.

Degree of difficulty: Medium

Last week: Congratulations to John Thompson of Murrumbateman who was first to correctly identify the location of last week's photo as the former site of The Railway Hotel on the northern end of Wallace Street in Braidwood.

The hotel was so-named in anticipation of the Tarago to Braidwood railway line which was touted by the NSW government in 1883, including a station near the hotel, but never eventuated. The hotel eventually went bust and had several subsequent uses, including as a lemonade factory, before being demolished.

How to enter: Email your guess along with your name and suburb to timtheyowieman@bigpond.com. The first email sent after 10am, Saturday October 31, 2020, wins a double pass to Dendy, the Home of Quality Cinema.

Good winter and spring rains in areas burnt by last summer's fires have resulted in a profusion of flowers in grasstree swales on the south coast like this one photographed by Sue Hines on the outskirts of Mallacoota. Wow.

On a recent walk along a creek line north of Yass, Jeevaka Wijesinha was stopped in his tracks by this 'Running Man'. Love it.

CONTACT TIM: Email: timtheyowieman@bigpond.com or Twitter: @TimYowie or write c/- The Canberra Times, 9 Pirie St, Fyshwick