Via Militaris or Via Diagonalis was an ancient Roman road, starting from Singidunum (today the Serbian capital Belgrade), passing by Danube coast to Viminacium (mod. Požarevac), through Naissus (mod. Niš), Serdica (mod. Sofia), Philippopolis (mod. Plovdiv), Adrianopolis (mod. Edirne in Turkish Thrace), and reaching Constantinople (mod. Istanbul).