For years the town of Sevastopol was closed to foreigners even to Ukrainians who couldn't show that they had a good reason for going there eg family or business connections. You had to have a permit, because Sevastopol was the home of the soviet Black Sea fleet, and at the height of the cold war the town was definitely off limits to western tourists. In 1997, Russia agreed to hand over control of the town to Ukraine, and now Sevastopol welcomes visitors.