It's been nearly 10 years since the last residents moved out of Brisbane's Walter Taylor Bridge.

Once known as the Indooroopilly bridge, the Brisbane structure still intrigues motorists crossing over it every day.

It was opened on Valentine's Day in 1936 after motorists became fed up with having to be ferried across the Brisbane river.

The Indooroopilly bridge first opened in 1936. ( Supplied: State Library of Queensland )

It was initially named the Indooroopilly Toll Bridge but was renamed after Walter Taylor, who designed and built it, in 1956.

It remains the longest span suspension street in Australia, built with the support cables initially used in the construction of the Sydney Harbour Bridge.

Today it still exists as the only habitable bridge in the Southern Hemisphere.

Three generations of the same family — descendants of the bridge's original toll master — lived in the Indooroopilly pylon for more than 70 years.

The price of the toll never changed, costing roughly about 5 cents to cross until it was eventually removed in 1965.

Today, about 35,000 cars use the bridge daily.

So what is it like inside?

Three generations of the same family lived in the bridge. ( Supplied: Brisbane City Council )

From the outside, the apartment seems as though it would be small, but once you step inside, it is surprisingly spacious.

There are 52 steps on either side of the structure leading up to the living quarters, where the ceilings are approximately 10 metres high.

Sorry, this video has expired Inside the kitchen and living area and the view from the verandah.

The walls in each bedroom don't go to the very top of the ceiling, so it wouldn't have been the most private living arrangement for the family — in fact the children who lived there often climbed over the walls to escape each other when playing hide and seek.

The hallway with two bedrooms on the left and verandah to the right. ( ABC News: Melanie Vujkovic )

Original tollkeeper of the Indooroopilly bridge, Morton John Green. ( Supplied )

Parts of the home have been renovated since it was first built, including the kitchen.

Mort Green was the bridge's first toll master, and lived in the Indooroopilly pylon from the first day the bridge opened.

His son later had seven children, who became the third and final generation to inhabit the bridge.

In total, it remained the family home for 74 years, until the last two brothers moved out in 2009.

One of the brothers had to be craned out of the apartment after ambulance officers were unable to carry him down the narrow stairs due to his physical condition.

Sorry, this video has expired Mort Green's sister, Elaine, and her husband George MacDougall lived on the Chelmer side of the bridge in 1954

The man had suffered a severe asthma attack and it took more than four hours to organise the rescue.

At the time the family remained very quiet about the incident, and they have rarely spoken to the media about what it was like living inside the bridge.

The ABC made efforts to contact the family, but at the time of publishing had been unsuccessful.

One of the brothers suffered a medical condition and had to be rescued by crane. ( ABC News )

Brisbane Greeters guide Blair Allsop has spoken to the family over many years as part of his research and said for them, life in the bridge was normal, and they continued to be surprised by the interest.

"It's just the old family home — if it wasn't part of the bridge then nobody would really be aware of it," Mr Allsop said.

Mr Allsop said the family still mostly lived in south-east Queensland, but not Brisbane, while others lived in Sydney.

The bridge remained empty until 2013, when Brisbane City Council eventually opened it to the public.

Thousands have since poured through the Indooroopilly pylon, as part of an ongoing guided tour by the Brisbane Greeters.

The same family lived in the home for 74 years, even after council bought the bridge. ( Supplied )

The bathroom inside the Indooroopilly apartment. ( Supplied: Brisbane City Council )

The Indooroopilly apartment's living quarters. ( Brisbane City Council )

What about the other side?

The Chelmer side of the Indooroopilly bridge was always considered the "less important" side.

When the Walter Taylor Bridge was tolled, the second-in-charge usually lived there.

The Chelmer pylon was rented out over decades, suffering significant damage. ( Supplied )

Later on it was rented out to various families, but when Brisbane City Council took over, it was mostly occupied by university students.

Over decades the pylon suffered significant damage from raging parties, and Mr Allsop said often the doors were left unlocked.

"Like most rental properties, the care and maintenance wasn't necessarily the best, so it got very badly knocked around," he said.

"There was graffiti inside, there's been damage to walls — it's not a very nice space."

What's different about the Chelmer pylon is that it has a community space, or ballroom, built beneath the apartment.

The Chelmer pylon has a community space, or ballroom, built beneath the apartment. ( ABC News: Melanie Vujkovic )

"It never really worked well as a community space because it had the road as its ceiling, and roads don't make great ceilings," Mr Allsop said.

"So there was always problems with leakage, noise, and it was never really a great space."

When you live in a bridge, what's your address?

The family's address was simply Indooroopilly pylon, Indooroopilly bridge. ( ABC News: Melanie Vujkovic )

This was the Green family's front door and their address was simply Indooroopilly pylon, Indooroopilly bridge.

The toll booth was located right outside the Green's apartment. ( Supplied )

"That's how they got their mail — it'd be one of the few houses in all of Brisbane that doesn't have an address," Mr Allsop said.

The toll booth itself was positioned on the Indooroopilly side, so the tollkeeper only needed to walk out the side door to get to work.

Hidden behind a wall in the pylon entrance was a safe where all the coins were kept.

The children's job every day when they came home from school was to count the day's takings.

Mr Allsop said although the family made their living off cars, it had not owned its own, and had no way of getting the coins to the bank.

"They had to contact the bank, and the bank would come with their armoured vehicle and collect all the coins," he said.

Dig far enough and you might find gold

When they were first building the Indooroopilly pylon, workers found gold about 15 metres underground.

It was only a little bit — less than a handful — but the concentration in the small area was quite strong.

"There is a gold vein that runs through here," Mr Allsop said.

"But when they found it, Walter Taylor had been working on the project for many, many years, and as soon as they found the gold he was like 'oh no, now my project is going to come to an end', so he went and bought all the mineral rights on this side of the river."

It was kept pretty quiet at the time, because the bridge was more important to Mr Taylor than the gold.

"When the city council bought this bridge back in 1965 … from the toll bridge company they inherited all the mineral rights, so one day if they ever put a tunnel through here, they could pay for it with the gold they find," he said.

Meanwhile, the cinema still located just down the road from the bridge was named Eldorado as a result of the find.

The Eldorado cinema received its name from the gold find in Indooroopilly. ( ABC News: Melanie Vujkovic )

What does the future hold?

Mr Allsop said the bridge would probably never be reinhabited as a home or commercial business, because it would need significant upgrades to meet today's building standards.

The stairs are too steep without any landings, there is no disability access, and the walls are so thick it would be very difficult to install an elevator.

The apartment has one of the best views of the Brisbane river from its windows. ( ABC News: Melanie Vujkovic )

For the foreseeable future, the Indooroopilly pylon at least will remain a tourist destination, while the Chelmer side may never be opened again.

"I think what it is, is what it is, and it continues to fascinate people because of the history of it," he said.

If people want to see inside the Indooroopilly apartment, tours can be booked via the Visit Brisbane website.