Rob Gronkowski's New England mansion sits behind a gate -- surrounded by spiked fencing -- with a security system ... but it wasn't enough to deter burglars.
The media has already arrived to Gronk's home to cover the story ... that the Patriots' home was targeted by criminals who raided the place while Rob was in Minnesota for the Super Bowl.
The Foxborough Police Dept. says it's investigating the incident and hopes to bring the crooks to justice.
Hopefully, Gronk has some sort of video surveillance system that can help the police -- but we couldn't see any cameras from outside the home.