In the course of the major restoration of Bremen Cathedral, important finds were made during archaeological excavations in 1974-1976. Well-preserved medieval bishop's tombs came to light, which were furnished with lavish grave goods.
The film "Bremen Cathedral - treasure trove of the past" by Fritz A. Bauchwitz for Radio Bremen from 1977 (approx. 23 min) illustrates the archaeological excavation work and the efforts of the restorers.
The film is in German. If you choose the option to watch the film on YouTube, you can select English subtitles there.