A collection of books on little-known facts about the Istana will be launched on Sunday.

Titled 150 Best Kept Secrets Of The Istana, the collection of three books will commemorate the 150th anniversary of the Istana and will be launched at its National Day open house by President Halimah Yacob.

The three books will also introduce readers to some of the inner workings behind state events in the presidential estate.

Completed in 1869, the Istana was built by the British colonial government to house its governors and was originally known as Government House. When Singapore attained self-government in 1959, it was handed over to the Singapore Government and renamed the Istana.

At the open house, President Halimah will also launch the second issue of the Istana Souvenir Series, which will feature four unique medallions showcasing the rich diversity of flora and fauna within the Istana.

Istana Cookies, which were launched on July 5, will also be available during the open house for those who make a donation to the President's Challenge.

The cookies come in five flavours, based on ingredients derived from spices and fruits found on the Istana grounds.

The National Day open house will also feature a PAssionArts Festival Village and other performances.

There will also be a guided nature walk and a guided tour of the Istana main building where visitors can visit selected function rooms and view collections of state gifts. Fees for the tours range from $2 to $10.

As part of the celebrations for National Day, open-house visitors are encouraged to dress in red and white. Entry to the Istana grounds is free for Singaporeans and permanent residents.