The 37-ton artwork has been billed as the largest and most spectacular piece of street theatre ever staged in the UK.
Created by French company La Machine, the installation cost £1.8million to bring to Liverpool – and all but £250,000 of this was funded by the taxpayer.
The story behind the artwork is that French 'scientists' have arrived in the city to investigate it.
They will use cranes to remove the animal off the tower block, before taking it to their 'research base' in Liverpool's new concert venue, the Echo Arena.
There, the creature will undergo a series of experiments, allowing the team to show off special effects using water, fire and artificial snow.
Organisers hope the spider will attract huge crowds, but onlookers appeared more bemused than enthralled.
Eric Wilson, 82, from West Derby, said: 'What the devil are they going to think of next? It's novel, I think some will like it. There's never a dull moment in Liverpool.'
His wife Dorothy, also 82, added: 'I wouldn't like to meet it in the dark. They say it's going to walk the streets but I hope I'm not down here when it does.'
And after one driver pranged his car trying to catch a glimpse of the creature, police warned motorists not to become distracted by it.