More than 300 people spent yesterday afternoon in Union Terrace Gardens, Aberdeen, which could be raised to street level and built over as part of multi-million-pound proposals backed by the city council.
Friends of Union Terrace want to protect the Victorian green space, which local oil tycoon Sir Ian Wood wants to redevelop.
Last month councillors voted 20 to seven for the 140 million "city square" project, which includes a 50m donation from Wood.
Campaigner Vicky Rider, 31, from Aberdeen, said: "A lot of people didn't think the council would vote as it did. We're all going to have to pay for this. What will people think of having a big building site in the middle of town?"