Kambah is four times the size of the average Canberra suburb, and the largest in the ACT.

It's also the subject of many Curious Canberra questions.

Ben Chapman, of Florey, started to wonder about suburb sizes after he started driving an Uber part-time.

"Just from driving around, I got to know really clearly how big Kambah was," he said.

He asked: Why is Kambah so enormous?

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Aden Cotterill's question was far more speculative.

"Is it really true that the suburb of Kambah is the largest in the southern hemisphere?"

"I've heard a lot of Canberrans say it… you start to believe it without actually ever checking the facts," he said.

Let's start with why the suburb is larger than most.

A new approach to planning

Former planners say the topography of the area contributed to the suburb's size. ( ABC News: Sonya Gee )

Jeff Brown, the Surveyor-General of the ACT, explained Kambah's size and origins.

"Kambah is our biggest division or suburb and it's 1,130 hectares," he said.

"The next biggest ones in the ACT are Symonston, which is 980 hectares, Fyshwick, which is 970, and Yarralumla, [which is] 881 hectares."

Ben asked Jeff if Kambah's size was the result of "a clerical error [made] by a public servant" who forgot to mark out individual suburbs.

"It certainly wasn't a clerical error... it was on the basis of the territorial unit concept," Jeff said.

"It was a little bit of a change of thinking from previous town centres."

The Kambah District Plan was published by the National Capital Development Commission. ( Supplied: ACT Government )

George Tomlins, a former Chief Planner for the ACT, explained the concept for Tuggeranong's first suburb.

"Rather than being a neighbourhood based on a school... it was a territorial unit based on the geography with a flexible spine of community facilities," he said.

Hills and ridges helped define Kambah's boundaries in the north, east, and west - contributing to its size.

Timing played a part too, planning for the suburb began in the early 1960s.

"Canberra was growing or had been growing at 10 [per cent population per year]... there was a need to provide a lot of housing and so there was an advantage in having bigger building blocks," George said.

The neighbouring suburb of Wanniassa was also based on the territorial unit concept.

New Canberra suburbs are considerably smaller and that's because the thinking has changed again.

"More recently than in those planning days of Kambah there has been a bit of thought… that the ideal size for a division [suburb] is around 500 hectares," the Surveyor-General said.

The largest suburb in the southern hemisphere?

The suburb was built in four stages but always considered as a single unit. ( ABC News: Sonya Gee )

Answering Aden's question was harder, which might explain why the rumour has been around for so long.

The Surveyor-General suggested I try PSMA Australia, a company that has put together its own comprehensive map of Australia by pulling together data held by state and territory governments.

It was originally known as the Public Sector Mapping Agencies.

Tom Spencer, a product quality manager at PSMA Australia, agreed to help out.

"We got one of our analysts to look into this problem. He probably spent two or three hours really digging through the data to understand if this is something we could do," he said.

The company compared Australian suburbs using its Administrative Boundaries collection, which captures suburbs and localities, along with government and electoral boundaries.

Tom Spencer from PSMA Australia used the company's comprehensive map to help answer the question. ( ABC News: Sonya Gee )

A problem arose early on.

"We have the localities and suburb boundaries for Australia, however there's no delineation between what makes a rural locality and what makes an urban suburb," Tom said.

The Gulf of Carpentaria originally topped the list of Australia's largest 'suburbs', along with two deserts in Western Australia.

"In terms of looking at it purely by our classification of an urban area, it [Kambah] was around the 120th mark," Tom said.

To make the comparison more meaningful, PSMA considered population size and density before coming up with another set of results.

"If we're looking at suburbs where the minimum population density is similar to Kambah's then it's around the 20-30 mark in the table."

The image below illustrates what PSMA determined to be the four largest suburbs in Australia that have a similar population density to Kambah, compared to the ACT suburb.

When compared to suburbs with a similar population density, Kambah was the 28th largest. (Source: PSMA Australia, Image: Ryan Kerlin, ABC News)

No matter which way PSMA looked at it, Kambah came "nowhere close to the top."

As to whether it's the biggest suburb in the southern hemisphere - that's now an easy no.