If you're at the Het Blauwe Hart ("The Blue Heart"), congratulations! You have arrived at the…read morehistorical Nieuwe Kerk ("New Church") and are either about to enter or leave the Delft Market Square!
This is a public art installation created by Marcel Smink placed on the loop of Oude Langendijk (street). It's a stylized heart symbolizing "the heart of the city" made from Delft blue glass to represent the city's trademark blue Delftware pottery and the stained glass windows of the historical buildings. It's pretty, pleasing to the eye, and lights up when it gets dark Kudos to Mr. Smink, it's a lovely piece of work.
Heads up if you're still in the process of planning or haven't visited the Royal Delft yet, there are many shops selling Delftware here. If you're in a tour group with limited free time, there are various places to eat and desserts to have in this square as well. Have fun in the Olde Centre with its restaurants, multitudes of souvenir shops, the Nieuwe Kerk, and the Standhuis Delft ("Delft City Hall").