Baidu map shows that the distance from Nanjing South Railway Station to Gulou Hospital is 13.8km, so you can take the subway. Take the subway line 1 from Nanjing South Railway Station (south of Baguazhou Bridge) and get off at Gulou Station (1 exit). Finally, walk 220 meters to reach the destination Nanjing Gulou Hospital. The whole journey takes 33 minutes.