Poibrene is located in the north-western part of the Pazardzhik Province on the left bank of the Topolnitsa river.
Topolnitsa is a village in Dupnitsa Municipality, Kyustendil Province, Bulgaria.
According to the Treaty of Berlin of 1878 the border between the liberated Principality of Bulgaria and the autonomous Eastern Rumelia followed the summit of the Balkan mountains and went southwards between Pirdop and Dushintsi eventually following the Topolnitsa river at Petrich.