Yes it does, quite regularly. Depending on where they are found and how huge the damage and danger could be, thousands of people have to be evacauated sometimes. in June, they evacuated over 18 000 people in Hannover to difuse 5 bombs. They don't look that dangerous to me, but looks can be decieving. There are probably still hundreds of tons of undiscovered unexploded bombs and other things like mines, handgranades, ammunition, barrels with toxic content etc. buried in the ground from both world wars.
I don't really know how you can check the ground thoroughly before say starting to digg the space for an appartment house, but when the city you build in has been bombed heavily during the war I think most contractors do. I remember a case in Berlin in 1994 where they didn't, and a sort of jackhammer digger (size of a digger but does what a jackhammer does, I don't even know the right word for that in German) was just burrowing into the ground when it hit a bomb. The blast killed 3 construction workers, wounded 17 and made a pretty big crater. It sort of stuck with me because one old lady that lived nearby said the explosion had sounded exactly like during the war.
It costs money to check beforehand and I guess some companies just rather take the risk.
Were it a book or shortstory, it would have been a form of poetic irony if some of those bombs under the parking lot in Stuttart had exploded; but I am glad they discovered them and nobody was hurt.
It is a bit difficult to teach the reality of a bombing raid and the war to young school children, but one man really gave his best. I think this happened around 2 years ago - an elementary school was having a project week about the war and what it was like and what happened, and the janitor of the school, an elderly man around 70 or so who was working pro bono and was a pyrotechnics hobbyist, rigged a sort of parcours in the school yard.. he installed loud sirens and loudspeakers and pyrotechnics effects so that it reproduced the noise of a bombing raid quite accurately. It must have been really really loud, with smoke and explosions and sirens - he traumatized those children, even though it couldn't have been even close to the real thing. That story always makes me grin despite its content because it's so bizarre and tragic and funny at the same time. Blackandwhite footage from falling bombs and pictures of bombed out cities don't really let you know what it must have been like during a raid, and even the approximation was too horrible to let children experience it.