A TRAVEL GUIDE TO EUROPEAN SCIENCE would proceed from London to Paris to Moscow to Amsterdam. These cities, according to Institute of Scientific Information (ISI), were responsible for the greatest number of published scientific papers during the period 1994-1996. If one ranks by per-capita output the order of top European cities becomes Cambridge, Oxford, and then Geneva/Lausanne, (information prepared by Christian Matthiessen of the University of Copenhagen and Annette Schwarz of the Technial Knowledge Center of Denmark.) In the field of physics the leaders in producing papers are Moscow, Paris, Geneva, St. Petersburg, and Warsaw. Narrowing further to condensed matter physics, the order begins with two Russian cities, Moscow and St. Petersburg, followed by Paris, Berlin, and Stuttgart. (Science, 21 August 1998.)