Where to fete a romantic fantasy about spanning time? Under a bridge, of course. On Dec. 16, stars partied at Guastavino's, a Manhattan eatery perched beneath the 59th Street Bridge, for the opening of Miramax's Kate & Leopold. Leads Meg Ryan and Hugh Jackman worked the room and played host to a diverse crowd of costars (Natasha Lyonne, Breckin Meyer, Liev Schreiber) and cohorts (Susan Stroman, Ian McKellen, Harvey Weinstein, and Matt Damon, who steered clear of fancy drinks in favor of beer). Jackman, the film's dashing duke from yesteryear, confessed he's not always so suave. ''My wife will tell youthe first time I rode horseback was probably the most unsexy display ever,'' laughed the Aussie actor, whose character rescues Ryan while atop his trusty steed. K&L scene-stealer Meyer also assured us that he too is nothing like his character. ''I don't need some guy from another century to tutor me about women,'' he quipped. Lyonne, holding court at a table with Saturday Night Live's Maya Rudolph, was way into characterand just not hers. ''Would I travel through time for love?'' she asked. ''Hell, yeah!''