"I just marvel at all of the ways various aspects of the building turns up on things over the years, like key ring tags and milk bottles and other kind of things, of everything from the curved walls to the flag masts," he said.

Mr Guida was one of the architects behind the iconic design of Parliament House, which this week is celebrating 30 years since it opened its doors.

Three decades on since its grand opening as part of Australia's bicentenary celebrations, Mr Guida said Canberra's most recognisable symbol was still just as impressive.

"For everyone involved, it was one of our finest achievements," he said.

Parliament House's iconic grassy hills and prominent flag mast weren't always a sure thing. The nation's federal politicians could just as well be sitting in a building shaped like a giant map of Australia.

Deep within the bowels of the National Archives, there are more than 300 alternate designs for Parliament House, all submitted as part of an international design competition.

With the existing parliament house bursting at the seams, and the dismissal of Gough Whitlam in 1975 sparking a revival in the Australian political process, archives curator Laura Cook says the late 1970s saw a renewed interest for a more permanent home for parliament.

"During the five-year period [after Whitlam's dismissal] there was a revival in the interest of an Australian symbol of parliament," she said.

From 1975 the National Capital Development Authority spent four years planning for a new, and more permanent, Parliament House, with a design competition announced  in April 1979.

Dr Cook says 961 architectural firms registered for the competition, each paying a $50 deposit and in return receiving a large blue book from the authority, outlining the process and the future significance of the building.

"The brief was so exact and descriptive. It had to cover everything from the loading dock, to storage space for toilet paper, to then also creating a symbol of democracy for the Australian people," she said.

While almost 1000 firms registered for the competition, just 329 submitted an entry for the first stage, which required a report as well as 10 drawings of the plans.

Just five designs were selected to advance through to the next stage, meaning some of the world's best architects missed out, including a design by renowned Australian architect Harry Seidler.

Among the designs that didn't make the cut were a spaceship-looking parliament, when if seen from above, looked like a giant map of Australia, complete with a bridge extending to a standalone Tasmania.

Out of the five that went through to the next stage, two of the firms were Australian, one from the UK, one from Canada and one from the US, however, all the teams had to have at least one Australian citizen.

If a design from a finalist firm from London, Bickerdike Allen Partners, had won, Parliament House could have looked reminiscent of a building out of Blade Runner, with a whole lot of concrete involved.

"All the finalists had the greatest potential to be further developed and the architects had a sympathetic approach to the natural environment," Dr Cook said.

In the end, it was this sympathetic approach that saw New York firm Mitchell/Giurgola & Thorpe take out the top honours.

While many people think that Parliament House is underground, Harold Guida sees it in a different way.

"It's a building with a grass roof in the middle. That form of making a landscape with the building is a very unusual one in architecture," he says.

"We had a big respect and regard for [Walter Burley] Griffin's plan for Canberra, and we wanted to engage with the plan and the city."

Designed by Romaldo Giurgola, the plan for Parliament House was announced as the winner on June 26, 1980.

Originally asked to be a panellist to select the winning design, Giurgola declined the offer, wanting to submit his own design for the national capital.

As a design co-ordinator, Guida was responsible for meeting with all the project's different teams to ensure a unified design.

"The design process was difficult, the parliament had lots of different uses and lots of functioning groups," he says.

"It required a fair bit of attention to keep consistency but to also allow symbolic differences to occur as you move throughout the building.

"What we intended was the front entrance to be without steps, so it gave access to parliament to the public where they could engage in the process."

It was the design's openness that curried a lot of favour with the assessors, who praised its accessibility in their final report for the selection process.

"It properly reserves the top of the hill for the use and enjoyment of the people of Australia," the report reads.

"So far from the new Parliament House glowering down, forbidding and inaccessible, people will walk and children will clamber and play all over its roof.

"A further attractive feature of the winning scheme is its simple imagery. It is capable of naive graphic representation: children will not only be able to climb on the building, but draw it easily too."

The report said the design kept with Griffin's original plan for Canberra, as well as being non-intrusive.

"Visitors can penetrate the heart of the building without intruding on users' activities or compromising security," the report says.

"Security should be able to be maintained with a minimum of overt "police presence"."

Construction began on the project in 1981, with a deadline of Australia Day, 1988, with the initial pricetag expected to cost $220 million. It would eventually open on May 9, the anniversary of the opening of Old Parliament House, with the final costings at more than $1 billion.

The original report estimated that up to 800 construction workers would be on site at any one time during the building phase. It's estimated that10,000 people were involved in the construction of Parliament House in some way.

Contractor Dave Cavill was one of them, who worked on the project in steel fixing from May 1982 until 1987.

"I worked all over the western side of the building, which was all of the Senate chamber and all of the Senate offices," he said.

"Our job was fixing the reinforced steel before all the concrete was poured into the columns. We had an average of around 12 people working in the team, but on some days it would be in the thirties."

Due to the size of the construction, both the design and the construction phases were undertaken at the same time, meaning the architects had to work quickly to keep ahead of the building efforts.

For Cavill, it meant that plans for the nation's parliament were constantly changing.

"You would get a drawing for a particular design in the morning, and then it would be superseded by plans in the afternoon, and this almost happened daily. Apart from that, it was a normal construction," he said.

However, the build wasn't entirely without problems, Cavill said. Parts of the project were built using American standards instead of Australian standards, making some of the fire doors initially too narrow.

The building also ended up being one metre higher than planned, with digging into Capital Hill stopped just short of the original target in order to meet the 1988 deadline

"Some of the doors they initially contained, because when it went to tender, it didn't specifically say that it had to be asbestos free in the contract," Cavill said.

"So for a while, all the fire doors in the building contained asbestos and they all had to be replaced."

While Cavill said he's worked on many major building projects in Canberra, Parliament House remained one of the most significant.

"We're all very proud of the work we did up there. It was a huge thing," he said.

From the moment it opened on May 9, 1988, Parliament House was already an instantly recognisable icon in Canberra.

The Canberra Times reported more than 25,000 Canberrans attended the opening, with the Queen officially unlocking the building.

Among the guests of honour were then-Prime Minister Bob Hawke, then-Opposition Leader John Howard, with the national anthem sung by Yvonne Kenny, and John Farnham being among the official guests inside the building for the reception.

The opening was also marked by a flyover of 12 RAAF jets, as well as a 21-gun salute.

While he initially lived in the US during his early years as an architect, Harold Guida now calls Canberra home and still works closely with the building.

"We helped to design the new fences and security modifications in the building over the past couple of years," he said.

"Like many things that have changed in the world since 1988, security is one of the most important aspects of public buildings everywhere in the world now."

Visitors may not be able to walk all the way up the hill and over the heads of their elected officials like they used to after the building first opened, but Guida was optimistic that it could happen again some day.

"The design of Parliament House was to have that accessibility, and we hope that one day in the future, probably not in my lifetime, but some day we'll be able to remove the fences."