A man charged after allegedly breaking into Old Parliament House told police he believed people were trapped inside and needed to be set free.
The 30-year-old Watson man was arrested about 1.20am on Tuesday after allegedly entering the building.
Police said buliding security told them a person had broken into the building by smashing some glass doors.
Officers searched the building but couldn't find him until an announcement was made on the building's internal PA system telling the person to go to the main lobby.
The man did so, and he was arrested.
Police have charged the man with trespassing on Commonwealth property and two counts of damaging Commonwealth property.
When the man appeared before the ACT Magistrates Court later on Tuesday morning, he was not formally charged and instead sent to hospital for a mental health assessment.
Appearing via video link, the man said he was "more than happy to pay the damages".
Special magistrate Margaret Hunter said the man would appear before the court after the hospital determined if he needed immediate treatment for a mental impairment.
The Canberra Times has chosen not to name the man until more information about his mental health is available.