For years, pedestrians on the popular bridge-to-bridge walk around the lake have scrambled to avoid being hit by traffic on Bowen Drive.

Now National Capital Authority chief executive Malcolm Snow said more people will be able to enjoy the precinct.

"This project has sets a benchmark for projects like it to encourage more activity and life in the parliamentary zone," Mr Snow said.

"It's part of an ongoing program of lakeside developments; we can definitely see future opportunities."

New landscaping, lighting and seating are some of the features of the redeveloped site.

The site also includes a new viewing platform where pedestrians can look out over the lake and a sculpture by Inge King on loan from the National Gallery.

The platform will also be an excellent vantage point to watch participants huffing and puffing their way through The Canberra Times Fun Run this Sunday.

Plans for the underpass were first announced nearly four years ago.

Its opening was to coincide with Canberra's centenary in 2013 however the authority put the project on hold in late 2011, due to unexpected major engineering works at Scrivener Dam.

Work commenced on the underpass in February 2014, but bouts of inclement weather and latent conditions delayed the $10 million project by six months.

Mr Snow described it as a "complex" project.

"We had to create tunnels but keep traffic moving," he said. "It was a challenge."

Senator Zed Seselja will cut the proverbial ribbon on the new underpass at 9.45am.

He said the crossing has certainly been "worth the wait".

"When I was in the ACT legislative Assembly, it was my standard run and you used to have to wait there for the traffic," Mr Seselja said

"I hope tens of thousands of Canberrans will enjoy the walk over the next few months."