The ACT came together after the Canberra Islamic Centre was hit by vandals who poured gasoline on the floor, trashed hundreds of books and spray-painted expletives on the walls.

ACT residents, embassies and religious leaders joined forces to help clean up the centre – now the capital's Islamic community wants to say thanks.

"We're using the open day to obviously get people to come to the centre, but also to thank the community who all came and rallied behind [us]," Canberra Islamic Centre president Azra Khan said.

"This is an occasion to thank all those who came on the Wednesday after the incident who helped us clean up the centre and showed their support for muslims in Canberra."

On Saturday, Australian mosques nationwide threw open their doors to non-Muslims as people across the country celebrated the National Day of Unity on Saturday.

In the ACT, the centre hosted a free lunch along with a number of events for children including pony rides, fairy floss and a jumping castle.

US ambassador John Berry presented the centre with a sapling from an oak tree originally planted in the Canberra embassy by Eleanor Roosevelt, 72 years ago.

"Today, Muslims in both the United States and Australia work with people of all faiths to build a brighter world," he said.

"Together we uphold our most cherished values – freedom, faith, community, justice, mercy and love."

Archbishop for Canberra and Goulburn Christopher Prowse spoke on the day, joined by a number of politicians including Canberra MP Gai Brodtmann, Multicultural Affairs minister Joy Burch and shadow treasurer Brendan Smyth.

Ms Khan said at a time of heightened terrorist alert levels and alarming rhetoric it was more important than ever for the community to come together.

"By the rest of the community coming together in this way it will [show] that we are united, and we are not going to let these individuals overseas dominate or create divisions amongst us," she said.