You wouldn't know it today, but this chaotic bit of town was once, back in Georgian times, the village of Ring Cross right on the edge of London. It still feels like a pause-point, a break in the continuity of this unforgiving highway. The university already has a landmark here in the form of two towers close to an important road junction, itself right next to the main railway line that thunders across at high level on its way down to the King's Cross terminus. A brutalist 1966 concrete tower from its polytechnic days - not bad of its kind, though scarcely inspired - was softened in 2000 by being placed in the embrace of an organically curving white sister tower by architect Rick Mather. Libeskind's contribution, just downstream of these, is entirely different. He has designed a ground-hugging building that plugs a gap - previously a mini-piazza - in the university's street frontage. This means that the campus now has virtually no public space, nothing to mediate between the roar of the traffic and the wall of buildings. On the plus side, the new insertion diverts your attention from some of the more humdrum university buildings behind. And, of course, it is an icon.

Iconography is the declared aim both of the university and of Libeskind himself, who openly uses the I-word when describing the project. Also the L-word - landmark - and the M-word - magnet. With all that going on, you might be forgiven for thinking this was a bit of public art rather than a building. It's a relief to find that it contains some real spaces. It has a lecture theatre, seminar rooms, staff offices and a café, so providing a focus for the university's postgraduate students. The interiors, though not exactly radical, are better than your average university block, enjoying unexpected views and interestingly swooping ceilings and tilting walls. The lecture theatre in particular has a hallucinogenic, German-Expressionism, Cabinet of Dr. Caligari feel to it. But the building's main purpose, it is quite clear, is to promote the presence of the university as an exciting place to be.