By the end of the war, the zoo was fortified with the Zoo Tower, a huge flak tower that was one of the last remaining areas of Nazi German resistance against the Red Army, with its bunkers and anti-aircraft weapons defending against Allied air forces. At the entrance of the zoo, there was a small underground shelter for zoo visitors and keepers. During the battle, wounded German soldiers were taken care for here by female personnel and the wives of zookeepers. On 30 April, the zoo flak bunker surrendered.