The lacy, opalescent dome of the Baha'i temple will startle you as you cross from Evanston to Wilmette on Sheridan Road. The mammoth, nine-sided structure, rising 191 feet, cuts an exotic profile against the low suburban skyline. This is the North American seat of the Baha'i faith, whose members follow the teachings of the 19C Persian prophet Baha'u'llah, believing in the "oneness" of religion and of humankind. Construction of the temple, which began in 1909, took nearly 50 years to complete.