See if it's possible to attend a worship service at Synagogue. You'll learn about some of the traditions and practices of the Jewish faith.
You'll be spoiled for sightseeing choice when in Ploiesti. Synagogue is an ideal place to start here, but there are plenty of other worthy attractions to discover. Central Market Hall, History & Archaeology Museum, and Ilie Oana Stadium are close to the Jewish house of worship and and will cap off your day nicely.