Melbourne's tallest building, the Eureka Tower, was completed 12 years ago but there's still one floor that's as empty as the day the last builder walked off site.

Level 85, only seven storeys from the top, is an enormous blank concrete canvas just waiting for a luxurious penthouse to spring up inside its glass perimeter.

Metal pipes are still visible running along the ceiling and PVC pipes protrude through the floor.

Aside from the enclosed central core of the apartment, which houses the elevator shaft, there are no internal walls.

That means there's nothing to block the panoramic views from Port Phillip Bay to the MCG, Royal Botanic Gardens, the CBD skyline, Yarra River and out to the Dandenong Ranges.

Architect Karl Fender helped lead the team from Fender Katsalidis which designed the 297-metre building, the second highest in Australia behind the Gold Coast's Q1.

Karl Fender's architectural practice Fender Katsalidis designed the Eureka Tower. ( ABC News: Nicole Mills )

Level 85 is yet to be fitted out or furnished. ( ABC News: Nicole Mills )

He said the 85th floor, still in its raw state, is owned by Melbourne property developer Elias Jreissati, who currently lives just a couple of floors below.

"His apartment was designed for him and his family, but as the family has grown and moved they find themselves in a very big apartment," Mr Fender said.

"This apartment has the opportunity to design around a lifestyle which is perhaps not so oriented towards housing family members.

"He no doubt has property in a number of places around Australia and he saw the value in keeping this and not using it to bring income; he didn't need to use it to bring income.

"He's in a privileged position of being able to wait and plan and get it right for the next stage of his life."

The 297-metre tower was opened in 2006. ( Flickr: George Bayliss )

The incredible piece of real estate will be open to the public as part of Open House Melbourne on July 28 and 29.

The bookable 30-minute visits will allow people to wander around the blank shell and admire the views and dream of their own penthouse lifestyle.

"This is quite unique because not very often does the general public see an apartment space before it has been fitted out," Mr Fender said.

"Here you see all the structural elements — you see cantilevered beams so we don't have columns in the apex of the windows, you see the mega columns that take the load of this whole building down to the ground, you see how the core works, how lifting works — before it has all been covered up.

"It's one thing to see a ceiling with lights and other equipment beautifully set out but this is the belly of it all.

"It's all very fascinating stuff I think and people enjoy to see that before it's all covered up."

Level 85 is the final shell to be fitted out and spans an entire floor of the Eureka Tower. ( ABC News: Nicole Mills )

Looking through the windows of level 85 of the Eureka Tower, you get amazing views of the city skyline. ( ABC News: Nicole Mills )

Mr Fender said walking through the space allowed people to imagine how they would use such a remarkable apartment if it was their own.

"It can be quite intimidating because you look at this space and you think, 'Oh, how would I plan this?'" he said.

"What it makes you do is interrogate your own view about your own living requirements, what your preference for view and aspect is, and how different spaces can engage with each other.

"There's a lot that goes into the designing of any apartment, but certainly one of a whole floor.

"In smaller apartments it's about efficiency of space, in bigger apartments it's about scaling it so the spaces do feel like home and suit your lifestyle."

To take a peek inside level 85 you must book a tour through the Open House Melbourne website.

The first ticket release is on July 13 and the second is July 20.

Large cantilevered beams running through the ceiling allow a view unobstructed by columns. ( ABC News: Nicole Mills )