Talk about a possible “boom” for tourism!

A Civil War-era cannonball was unearthed yesterday near the ferry landing on Governors Island, authorities said.

The 350-pound, 12-inch round projectile was discovered at around 8:50 a.m. by hardhats digging with a backhoe behind the seawall, said a spokeswoman for the Trust for Governors Island.

Students who attend the New York Harbor School on the island were rerouted around the site, and the solid iron cannonball was deemed safe by the NYPD Bomb Squad, police said. It was relocated for eventual display.