Secretary of State Hillary Clinton warned in May that Iran was building a mega-embassy in Nicaragua. The Washington Post can't find any evidence of any building site ("Iran's Rumored Nicaraguan 'Mega-Embassy' Set Off Alarms in U.S.", Washington Post, 2009-07-13) Some right-wing think tanks are perpetuating this myth.
The problem is that not only does the mega-embassy not exist or is even planned, but all the big talk of aid and investment from President Ahmadinejad has not resulted in any major projects.
What really gets me is the double-standard American politicians of any stripe use. Why is it OK for the U.S. to build a mega-embassy in Iraq, a few hours drive from Tehran, but it is not OK for a country the U.S. government doesn't like to extend its interest, like in Managua, a "48-hour drive from Brownsville TX" (Ronald Reagan).