The A.L. Cole Pumphouse at River Landing is one of Jeff O'Brien's favourite buildings in Saskatoon.

"This is hands down, one of the coolest places you will stand in," says O'Brien, the city's archivist.

"It's the only octagonal tower in all of Saskatchewan and probably one of the oldest industrial structures in all of Saskatchewan."

Saskatoon city archivist Jeff O'Brien said the pumphouse is the octagonal tower in Saskatchewan. (CBC News)

The pumphouse is one of 21 buildings set to open to the public Sunday for this year's Doors Open Saskatoon put on by Tourism Saskatoon.

The free event runs from noon to 5 p.m. CST. The public will have a chance to see inside buildings that are usually closed to the public.

Some other properties opening to the public include the Marr Residence, Fire Hall No. 1, the Delta Bessborough Hotel and ALT Hotel.

CBC tagged along with O'Brien for a sneak peek into the venerable old pumphouse.

Old machinery remains in part of the pumphouse. (CBC News)

Built in 1911, the pumphouse supplied water from the river to cool the power plant generators at the Saskatoon Power Plant and later the A.L. Power Station.

An addition was built in 1929 when SaskPower bought the building from the city.

O'Brien said the pumphouse was used to pump water to cool the generators of the electrical plant.

It's also a glimpse into the early days of Saskatoon, when the city doubled in size almost overnight in the early 1900s.

"You can't have a city without power," O'Brien said. "You can't have industry without power. And so in the early days of Saskatoon and every other city in the world it is looking for cheap electricity to attract industry.

He called it a symbol of the hopes and dreams of early Saskatoon.

"When opportunity was knocking and people were going, 'How are we going to grab opportunity? How can we make it dance to our tune," he said.

"So when you stand in this building, that's what surrounds you."

A map of the 21 buildings open to the public this Sunday. (Handout)

Catherine Kambeitz, Saskatoon's heritage and design co-ordinator, said there are plans for the pumphouse to open its doors again permanently, though in a different capacity.

"There is a concept plan for this area and specifically that plan would like to see this building re-used for a restaurant/bistro/cafe type of use," Kambeitz said.

"It's along the river, the location is fantastic. It's got that brick, octagonal tower which is fairly synonymous with Saskatoon. It is just a beautiful building."

Saskatoon's heritage and design co-ordinator Catherine Kambeitz says Doors Open gives the public a peek behind the curtain of some of the city's most important buildings. (CBC News)

There is another parcel that is for sale near the pumphouse and the city would like to see something built there and then hopefully have people in the area to support a restaurant.

The Doors Open event began in 2005 and has been presented every second year since that time.

Buildings of architectural and historical significance open their doors to visitors for a day. Many places provide guided tours or put on special exhibits or displays.

"It is an opportunity essentially to showcase Saskatoon's heritage and some of the great buildings that we have," Kambeitz said.