Complex sentence: Rădăuţi was one of the larger cities of the Duchy of Bukovina during the period of Habsburg administration (1777-1918), when time it saw a high level of German (especially Swabian) immigration.
Split into simpler sentences: Rădăuţi was one of the larger cities of the Duchy of Bukovina during the period of Habsburg administration (1777-1918). During that time it saw a high level of German (especially Swabian) immigration.