After many years of being closed to the public, the Prospect Air Raid Shelter will reopen this weekend.

Members of the public will be invited to tour the new ground level garden, and on Sunday only will be given the opportunity to peek inside the decrepit shelter.

Graffiti vandals and water have left their marks over the years inside the shelter. ( ABC Radio Adelaide: Brett Williamson )

The structure was built in 1942 as a wartime communications centre for the area.

Since being decommissioned it has housed a slot car club, was used for St John Ambulance training, and at one time was a ham radio operators' centre.

But after a rising water table flooded the building, it was deemed unsafe and fell into disuse.

"These are unique ... I don't think there are any other left in other states," Prospect RSL sub branch president Neil Rossiter said.

"South Australia was at the forefront of these sorts of things and this is a part of history we'd like to hold on to."

The original floorplan for the shelter. ( Supplied: Prospect Local History Group )

The shelter is one of only four left in the Adelaide area, with the remaining three at South Road in Torrensville, Rugless Terrace in Glenelg and Oxford Terrace in Unley.

"This one and Glenelg are the only ones to have public access," Mr Rossiter said.

The new gardens line the eastern side of the Prospect shelter and feature several seating benches and information boards highlighting the site's history.

"We are going to have interpretive boards so people can walk around the air raid shelter, read its story and reflect on what the story was 75 years ago," Mr Rossiter said.

"This is the first stage [of restoration and remembrance] and hopefully it won't be the last."

At one point the shelter was filled to a shin-deep level of water, damaging the paint and fittings.

Mr Rossiter said although the water damage was visible, the building still appeared to be quite sound, and the addition of a sump pump from the Prospect Council meant further damage would be avoided.

Repairing water damage and covering graffiti is next for a full restoration. ( ABC Radio Adelaide: Brett Williamson )

"Unfortunately it has been vandalised," Mr Rossiter said.

"We're hoping to clean it up and use it as an interpretive centre, a little museum or a Fringe or SALA venue."

Mr Rossiter also hoped people who had used the shelter over the years would come forward and share their stories.

"Once a building is gone, the future generations will never know what it was," he said.

"We lose part of our soul if we lose these sorts of stories."