A rally led by climate campaigner Greta Thunberg cost a council more than £10,000, new figures have revealed.
Thousands of people attended the event which started on College Green and was followed by a march through Bristol.
The bill included costs for closing roads, for toilets and for 10 crowd control barriers.
Mayor Marvin Rees was asked why a "less sensitive" location was not used but he said organisers were "insistent" on using College Green.
"Alternative hard-surface sites were suggested to the organisers but they were insistent on the event taking place on College Green," he said.
"We know these demonstrations cause a lot of disruption and we're grateful for people's patience and understanding as we balance and protect the rights of people to protest."
The bill was revealed through a written question by councillor Richard Eddy to the mayor, the Local Democracy Reporting Service said.
The toilets and barriers cost £1,051, security at City Hall was £2,340 and road closures and management cost £7,000.
It is not yet known how much the Youth Strike 4 Climate rally cost Avon and Somerset Police.
The grass on the site was damaged because of poor weather on the day of the rally, but it has since grown back.
A crowdfunder raised £25,000 to repair the "superficial" damage to the grass, and the money left over will be spent on wildlife and biodiversity projects across Bristol.