Russian forces retreated from the Ukrainian city of Kherson last month, dealing a major blow to President Vladimir Putin's war efforts, but marks of the eight-month occupation remain.Kherson, a regional capital, was the first major Ukrainian city seized by Russian forces after the invasion in February.Ukrainian officials have also helped some residents evacuate the liberated city ahead of winter as its power infrastructure has yet to fully recover from the battering."To give you an idea, during the month of our work, we found and removed several tons of mines," a Ukrainian service member on a demining squad told AP, adding that the mines were spread across nearly 4 square miles.Demining squads are still working to clear the city of traps left by Russians, like explosives left in potholes or buried in soil, but the freezing winter is making the work more difficult."