They still dot the woodlands of grand old English estates. That's because erecting a 'folly' in the landscape was a popular fad in 18th century England.

You wouldn't think you'd find many follies in Australia these days as they were often built in the form of a sham Gothic or classic ruin.

Who would want to construct a deliberate ruin whose sole purpose was to be either a romantic or picturesque sight?

Even Mrs Macquarie, the wife of early colonial governor Lachlan 'the builder' Macquarie, wasn't immune to the trend.

Macquarie was the Sydney governor from 1810 to 1821 who had a mania for building things and naming places after himself (Lake Macquarie anyone?).

Lesser known, however, is that his good wife brought some pattern books from England to add variety to colonial building styles.

Her influence is credited with Newcastle once getting a lighthouse above present Nobbys built in the bizarre style of a pagoda.

A sketchbook from the period hints that Mrs Macquarie once had a folly built. If she did, it hasn't survived.

However, that didn't deter artist Fiona Hall from creating a contemporary tribute that was installed in 2000 in Sydney's Royal Botantic Gardens.

Titled A Folly for Mrs Macquarie, the skilful artwork is an alternative gazebo made of a wrought iron domed roof above a curved sandstone base.

Look closely and you'll find an axe, wire and even bones, which don't seem out of place. All in all, surprisingly impressive.

Another Aussie surprise, which seems at first glance to be a home-grown folly, is down south about 160 kilometres from Sydney in the Kangaroo Valley.

But it has a very practical purpose, even if it looks a trifle overdone.

It's the Hampden wooden suspension bridge, with its Victorian-era architecture a nod to a past romantic epoch. The 1896 timber-decked bridge, built originally to service dairy farmers and cedar loggers, is built in the form of a castle.

Now a tourist attraction, it features four elaborate sandstone towers as if the portcullis is about to be lowered. If it's a folly, it's a great one.

Holy smoke! There's yet another one. It's at suburban Northbridge, only seven kilometres from Sydney's CBD. Northbridge's now state significant structure was opened to traffic in 1892.

The mighty steel suspension bridge comes with tall, sandstone turreted towers and was erected by private residential developers to encourage land sales after a new tram service was started. It didn't come. The bridge was then given to the NSW Government in 1912.

Closer to home in the Lower Hunter, and still raising eyebrows of visitors today, are the unusual stone structures built at Tanilba Bay, off Lemon Tree Passage Road.

Eighty-nine years ago, it was a very isolated site in the hot, dry bush. It could be reached only by a corrugated dirt road in a Ford Model T, or by water. That, however, didn't deter day trippers coming from as far as the Coalfields to ogle at some strange new structures.

When two sets of huge stone gates were erected here in 1931, they must have seemed like a true folly created at the height of in the Great Depression by someone with more money than sense.

But that assessment's far from the truth. Both huge ornamental stone gates were the brainchild of Henry F. Halloran (1869-1953), real estate developer, surveyor and landscaper extraordinaire.

He was canny as a fox, and built the gates (like the massive Northbridge 'castle') not on a whim, but as a clever real estate lure for punters to invest in his dream. His 'patriotic sub-division' of Tanilba Bay recalled WWI, which had ended just 13 years earlier.

Centred on the Avenue of the Allies, the estate featured names such as Diggers Drive, with the new suburb's entry and farewell gates leading up to his scenic weekender, historic Tanilba House (from 1831), on the point overlooking the Port Stephens waterway.

The elaborate 1931 stone entry gateway - the Portal to the Peerless - about 50 metres long with 12 portholes, is advertised as the Centenary Gates, marking 100 years from a pioneer settlement here in 1831 to 1931.

Travel down a pine tree-lined corridor to the distant second impressive gateway, the Water Gate, also from March 1931. It's totally different, taller and more ornate with multiple stone arches and a road spanning sign.

A special feature of this second "folly" are the bollards of the HMAS Sydney mounted atop the central pillars. The former warship was the victor in Australia's first naval battle against the German raider Emden in November 1914 in the Indian Ocean. Later, it had been moored in Port Stephens before finally being scrapped.

Down the road a little further and also designed by the flamboyant Halloran is his odd mosaic Temple of the Stork, another masterwork.

Close by are numerous other stone walls and carefully crafted stone pillars. The overall plan seemed to give the impression of early convict work.

There, the story might end. But is there another great folly left to investigate? Yes, there is and it's also linked to the remarkable, energetic Halloran and Tanilba.

While his rustic stonework at Tanilba made it the most famous of his port development plans, just as eye-catching, but virtually unknown today, are what's left of Halloran's grand dream deep inland.

Devised in the 1930s, it looks at first glance today like a giant folly. But looks can deceive. Halloran thought big. He aimed to create a giant suburb on the outskirts of present Canberra, called Environa.

Alas, his concept was thwarted by the Great Depression.

All that remains in a big sheep paddock today are an avenue of mysterious stone pillars, not unlike red mini-pyramids, a lone 12-metre high obelisk, walls, two timber bandstands and a colourful multi-stone archway, an echo of items surviving at Tanilba Bay.

About 1700 blocks of land were planned, but the dream evaporated. Today the site is privately-owned grazing land preserved intact by the Halloran family.