Alicia Keys' hubby, Swizz Beatz, certainly knows how to make his wife smile while she's working abroad 

Alicia was performing in Milan Tuesday when Swizz and their kids surprised her with the massive bling -- a piece made possible by Celeb Jeweler Elliot Eliantte.

We're told at about 150 cts, the Egyptian-themed necklace set Swizz back about $400K.

The baguettes around the main piece are set in a brick formation like the Great Pyramids.

The pendant is designed after Nefertiti, the queen of the 18th Dynasty of Ancient Egypt, but with Alicia's face on it. 

Nefertiti stands for strength, power, and beauty, while the infinity links symbolize eternal life.

It's a pretty sweet gift -- and this girl's been on fire for a while, so it's well-deserved 

 Alicia performed at the Queen's Platinum Jubilee last month, sharing the stage with the likes of Elton John, Diana Ross, Alicia Keys, Duran Duran, and other awesome acts.