EVEN as a week of non-stop partying climaxed at last night's ball at the sumptuous Taurida Palace, organiser Ted Marr wasted no time in naming the venue for next year. When the first guests to arrive met over dinner at St Petersburg's Shanghainese restaurant earlier in the week, Marr let it slip that the 1994 ''China Coast'' Ball was planned for the Victoria Falls hotel in Zimbabwe. And he confirmed the plans to the 350 revellers last night. Marr's announcement followed an annual tradition - he surprised guests at last year's ball at Shanghai's Peace Hotel by revealing the next venue would be in Russia. Although the annual event's venues appear to be getting more ambitious each year, Marr said the Zimbabwe hotel - a fabulous colonial reminder - had been in his sights for the past two months. As if to reinforce the fact, an unexpectedly large Zimbabwean contingent turned up in St Petersburg - including Maureen Summerfield, jewel company millionairess and one of the country's richest remaining expats. In St Petersburg, the guests have been doubting this bash could be topped. For five days, the local population has been treated to the sight of visitors to their fair city pushing the boat out at a different venue, then spilling on to the streets - stilllight at midnight due to the long summer nights - in black tie and fancy dress. Last Wednesday, at the Yusupov Palace - where Rasputin met his fate - the St Petersburg State Symphony Orchestra gave a private white-tie concert. On Thursday, Marr lined up the K2 dacha, the communist-built residence for visiting dignitaries - for a champagne reception. Friday saw the guests descending in turn-of-the-century Russian dress on Catherine the Great's stunning country palace outside the city for a garden party, followed by a private opera at the Hermitage Theatre in the evening. By the end of that day, guests were already looking the worse for wear,but the closing all-nighter at the Taurida Hotel - home during the day, no less, to the CIS interparliamentary assembly - saw the drinking and dressing up reach a spectacular peak.