Overnight a tower sprang up in the city park - where there had been none. And a girl ran from it, seeking help. But the price of her rescue could mean destruction to that town not once but three times over. For the tower was a time-bridge that brought a tyrant's future metropolis face to face with a piratical colony of the past - to make today's city their battleground! (from the back cover of the Ace Books first American edition)
Source · ISFDB CC BY 4.0