London had its elephant, and now Liverpool has its very own spider. At 7.36pm, a giant yellow leg appeared from behind a building at the end of Salthouse Dock and a crowd who had been growing increasingly restive after standing for 90 minutes in the pouring rain screamed and shouted.

Several children tried to hide, but one enquired if he might be able to take the spider home. "I wouldn't want that in my house," declared his mum.

"You wouldn't get it in our house," said her husband.

"It's like something out of Doctor Who," said another, as first more legs and then, slowly, a vast body emerged and a 50ft high spider started walking down the road, waving its great legs over the heads of the crowd.

There were more squeals: some of apprehension, others of sheer joy. The spider, named La Princesse, is the brainchild of François Delarozière and his company La Machine, who over the past 15 years have engineered a host of mechanical animals including the glorious Sultan's Elephant that made London smile in 2006.

This is his first spider, and its appearance is part of the city's capital of culture celebrations. Even on this dreary, rain-soaked Friday evening, many more will have seen the spider than the nearby Playhouse will be able to accommodate for the entire run of Pete Postlewaite's upcoming King Lear.La Princesse is a big girl, weighing 37 tonnes, and a marvel of engineering. She has 50 hydraulic axes of movement, took a year to build, and trundles along the road at two miles an hour.

Like most royalty she is demanding, and requires 16 cranes, six forklift trucks, eight cherry pickers and 250 crew to get about. What she doesn't exhibit as yet is a great deal of personality.

Even when given a bath in Salthouse Dock with the aid of some giant water cannon, she seemed curiously passive; but perhaps she was planning how to escape a demanding schedule of public appearances over the weekend which includes a water ballet in Derby Square and the ascent of Concourse Tower, before the finale on Sunday night at the entrance of the Queensway tunnel.

The element of surprise accompanying Sultan's Elephant (it materialised, as if by magic, out of nowhere) is inevitably missing here. The whole of Liverpool seems to know the city has a strange visitor, and, judging by Friday's turnout, it appears that the entire city wants to see it. Whether they will remains to be seen.

At the dock many - particularly those with small children - were defeated by the weather and the difficulties of getting a remotely good view. But on Saturday the spider goes on walkabout in the city centre, and, if the sun comes out, the odds must be short that Liverpool will fall for the charms of its spider just as London fell in love with its elephant.