Thousands of residents of Poland’s main southeastern city were evacuated from its central area on Friday after construction workers stumbled upon an unexploded quarter-tonne aerial bomb from World War II. During World War II, Wroclaw was a German city and was known as Breslau. It saw heavy fighting and widespread destruction, coming under heavy Soviet bombardment before Germany’s surrender. As recently as 21 May, a smaller unexploded bomb was found near the railway station in Poznan. Could there be other undiscovered bombs?