Viewing the trees and the rolling hills from a pavilion at the Arboretum's Village Centre, Yarralumla resident Luba Thompson observed: "It's real vision".

"I won't be alive to see the trees in their full glory but you can imagine, in time, that it will be absolutely superb," Mrs Thompson said.

"I think it's fulfilled the Burley Griffin initial plan.

"Even though Jon Stanhope copped a lot of flack, I'm pleased he pushed it through."

If visitors arrived at the Arboretum's opening festival with doubts on Saturday, those doubts quickly faded.

Early estimates put the crowd that came to see the culmination of a decade of work, born from the ashes of bushfire, at 15,000.

The day was unseasonably cool, but the winds were perfect for dozens of kite flyers that dotted the hills above Lake Burley Griffin.

Other guests jumped on buses for guided historical tours of the 250 hectare site, or took walks through one of the 100 forests and their 40,000 trees.

Sydney residents Josie and David McNeilly came to see the Arboretum's world-class bonsai display.

By the afternoon, they were already considering an annual visit to track the progress of all the trees.

"We came down just shortly after the fires originally and then someone told us about the plans," Mrs McNeilly said.

"It was hard back then to visualise what it would look like. Our minds are just blown."

Weston couple Cath and Andy Collins took their children Patrick, 4, and Samantha, 1 to the open day.

"It's fantastic, it's great," Mrs Collins said.

"We were just saying it's going to be an amazing place in 20 years' time."

National Arboretum general manager Jason Brown said visitors on Saturday conveyed "a sense of excitement and surprise at how beautiful the site is".

"Many, many people have been experiencing all the different things on offer for the day," he said.

"The music has been very successful, the art workshops for the kids have been very successful, but I think most of all it's very good to see people who are positive and happy and they've embraced the arboretum as their own."

Friends of the Arboretum chair, Jocelyn Plovits, managed the 150 volunteers at Saturday's celebration.

The volunteers will run guided tours every day and Ms Plovits said she felt like "nine years of gestation was finally over".

"This is literally a once in a lifetime experience,'' she said.

LISA COX