Three American hikers were detained last week by Iranian officials . A handful of tour operators provide tours for Americans to visit Iran . The Associated Press contributed to this report. Travel warnings for Iran have been in place since the 1979 hostage crisis .
Three American hikers were detained last week by Iranian officials . A handful of tour operators provide tours for Americans to visit Iran . A U.S. passport is valid in Iran ; visitors need a visa . Travel warnings for Iran have been in place since the 1979 hostage crisis .