For the seventh year running the Canberra Brick Expo has put some of the country's best block-based creations on display, attracting crowds young and old.

The Brick Expo, which runs across the weekend, raises money for the paediatrics ward at the Canberra Hospital.

Chairman David Boddy said some of the pieces on display took immense amounts of work to create.

"We have moving trains, and great ball contraptions and really technical models," he said.

"Engineering pieces like the Golden Gate Bridge, which is 15 metres, which is quite a feat, it's just stuck together with Lego, there's no glue or nails or wire holding it up — down to just very clever use of parts.

"They spend a lot of time and money and as you look around it's a testament to their creativity."

A tribute to Play School on its 50th anniversary was one of many pieces on display. ( ABC News: Greg Nelson )

The expo also opens its ranks to young people, who can show off their designs.

Seven-year-old Bianca Pasquariello won a prize for her Lego creation.

"I created a forest and it was called friends of the forest, and it has lots of animals and it's colourful … it took a few weeks," she said.

The expo raises money for paediatrics at the Canberra Hospital. ( ABC News: Greg Nelson )

Mr Boddy said the event continued to attract attention because of the creativity of its contributors.

"We try to bring a lot of new content every year, we have builders from all over Australia bringing their creations to Canberra, and for a lot of people this is the only place that you can see them," he said.

"We wanted to give Canberra an awesome event — a good family event — but we also wanted to showcase the great designers from around Australia."

Eight-year-old Alastair Cheung built a tank for the expo with his brother, and said he loved Lego because he could build anything he wanted, then smash it.

"You can buy it, then build it and destroy it and rebuild it, then destroy it … then build something new out of it," he said.