Detailed plan of Shanghai.

During the 1920s and 30s Shanghai had become the most important port in Asia, with tea, silks and porcelain being exported to Europe and America, and a great deal of opium being imported. The city was home to some 3 million inhabitants, of which 70,000 were foreigners. Although small in number, the foreigners (mainly British, French, American, Russian and Japanese), due to land concessions - which are clearly delineated on the map - controlled almost half the city and much of the import and export trade. What is not marked on the plan, however, are the city's notorious opium dens and whorehouses; with such earthly temptations well catered for and no passports or visas required, Shanghai became an infamous and exotic port of call.