A strong wall and bastions, with a broad moat and outworks, and forts on the surrounding heights, give the city an appearance of great strength.
The duchy of Warsaw and the fortress of Danzig formed new outworks of his power and enabled him to overawe Russia.
The long straight lines of works which stretched to the plateau of the Michelsberg and formed the outworks of the main fortress on the left bank of the Danube were purchased in 1900 by the municipal authorities, in order to be levelled and laid out in streets for the extension of the town in this direction.
The old outworks have been partly demolished and replaced by modern forts, while suburbs have grown up round the inner walls and bastions.
By his orders castles were built at the mouth of the Don and on the bank of the Dnieper, outworks against the ever-aggressive Tatars, as well as on either shore of the Dardanelles.