City Council staff were baffled by a mysterious trail of pink hand prints which appeared across Guildhall Square.
Nobody knew where they came from, or who made them.
A council spokesman said: ‘We think that they have been painted rather than chalked and they go right across the square.
‘The first time people saw them was when they came in to work yesterday.
‘It is quite incredible to think of how the prints got there, because it must have taken a long time to paint them.
•Pictured: Pink handprints leading from Portsmouth and Southsea station to the Portsmouth Polytechnic School of Architecture and inspected by architecture students Lynsey Smith, left, Brian Dawes and Barbara Howes.