A large-scale, free event featuring theatre and performances will take over London's Square Mile on 15 October.
The event is set to feature more than 100 performers, with a mass treasure hunt, three carnival-inspired fairs and creative street theatre planned.
It is the first major event planned by the City of London Corporation under its new flagship Destination City programme, designed to promote Square Mile's leisure offer.
Backed by a £2.5m annual investment from the City Corporation, Destination City plans to "drive the Square Mile’s recovery from the pandemic, revitalise its streets, reinvigorate its businesses, and boost its attractiveness to talent".
Policy Chairman of the City of London Corporation Chris Hayward said the event is "set to become one of the capital’s cultural highlights of the year".
"We will open the Square Mile’s doors to everyone, revealing fascinating secrets and making magical moments happen for our visitors."