The renovation of the run-down building began in 2011, thanks to a committed group of local history enthusiasts who managed to secure EU funding.
Since March 2013, the edifice has functioned as the The Museum of Masovian Jews (Muzeum Żydów Mazowieckich).
''What seemed impossible, turned out to be possible,'' Chief Rabbi of Poland Michael Schudrich said on Thursday evening.
Schudrich reflected that such endeavours can bear fruit when ''good people meet who want to work together.
''I want to thank all the good people here in Płock.''
The Torah ark was the only original feature from the synagogue's interior that had survived the war, and it had been exhibited elsewhere in recent years.
Known as the Aron Kodesh in Hebrew, it holds the Torah scrolls and is typically placed against the wall that faces Jerusalem.
In 1939, Jews made up about a third of the town's 9000 inhabitants, and the 900th anniversary of the Jewish community in Płock was being prepared.
However, the invasion of Poland by the Nazi Germans sounded the death knell for the community. A ghetto was created and most of the town's Jewish inhabitants perished in death camps.
Marchers commemorate the 74th anniversary of the liquidation of the Płock Ghetto. Photo: PAP/Marcin Bednarski
Anniversary of the liquidation of the Płock Ghetto
Thursday also saw a march commemorating the 74th anniversary of the liquidation of the Płock Ghetto, which was completed on 1 March 1941.
Jakub Guterman, who currently lives in Israel, was a 6-year-old boy at the time of the liquidation.
In an interview with the Polish Press Agency (PAP) he recalled the screams and gunshots of the round-up.
''Let us remember and not spare any strength to fight for a better world without prejudice, nationalism, racism, and hatred,'' he said. (nh)