https://www.oldenburg-tourismus.de/angebote/digitaler-stadtspaziergang
In order to get to know the city better, there are several guided, with a fee, city tours:
City walk through Oldenburg, 6€
City and palace guide, 9€
City tour by Bicycle, 12€
More information and tickets at: Touristinfo / Ticketshop, Lange Straße 3, https://www.oldenburg-tourismus.de/erlebnisse#/fuehrungen