Wednesday marked the 25th anniversary of one of the craziest and costliest art heists of all time. The brazen pilfering of half-a-billion dollars worth of masterpieces took place at the Isabella Stewart Gardner Museum, located in the Fenway.

Early in the day on March 18, 1990, two thieves dressed as Boston Police gained entry to the museum by tricking a security guard and stole 13 works of art that are now estimated to be worth $500 million.

The heist has yet to be solved and has spawned plenty of conspiracy theories. It is believed by some to be the largest monetary theft of private property ever.

The museum itself admits that two thieves arrived dressed as police and told a night guard they were responding to a call. The guard broke protocol, allowed the duo to enter the museum. Once in the building, the two told the guard there was a warrant out for his arrest, according to the museum, and that he should summon the other guard. He did so, without hitting the alarm and the two were cuffed and taken to the basement of the museum, where they were secured to pipes. Their hands, feet and heads were duct taped. Guards discovered them the next morning.

During the night, the thieves took 13 pieces of art, including a three pieces of Rembrandt’s work from the 17th century, Vermeer’s The Concert and Edouard Manet’s Chez Tortoni.

The investigation into the thefts continues, as the thieves have flummoxed the FBI and the U.S. Attorney’s Office for more than a quarter century. The museum, meanwhile, continues to offer a $5 million reward for information leading to the recovery of the pieces in good condition