Construction workers have unearthed a collection of wine over 50 years old in a German cellar along with a letter explaining the purpose of the unusual time capsule.

The construction work took place in a wine cellar in the district of Oberrotweil in the town of Vogtsburg in the German state of Baden-Wuerttemberg where 37 hidden bottles from the 1970s were discovered during building work.

According to the winery owner, the Riesling, Pinot Noir and Silvaner wines were discovered “in a small hollow in the middle of the tunnel” dug by the construction workers.

Buried with the wine was a message in a bottle from three men named Gerhard Kiefer, Erwin Kalser and Roland Fischer who dug a tunnel between two wine cellars on the estate around 50 years ago, according to Johannes Freiherr von Gleichenstein, owner of the cellar and the Freiherr von Gleichenstein winery.

The letter reads: “This wine was buried during the construction of this tunnel on 14th February 1974. If this wine is found, the builders ask for a reply message.”

Johannes said he contacted the tunnel diggers and learned that one had died and the other two were very happy to hear from him.

He said: “We didn’t know about the message inside the bottle, although we anticipated that some old wine bottles might show up.”

The cellar owner explained that “the wines have more of a sentimental value rather than a material one”, since they date back to a time when his father was still in charge of the winery.

He added: “The men saw their treasure as a kind of historical document so that someone would one day remember who laboriously dug the tunnel back then.”

The find took place during works to increase the cellar capacity from 140,000 litres to 440,000 litres as it has become too small over the years.

Johannes said: “This is how we planned to provide high-quality wines with more time to mature in stainless steel tanks.”

The tunnel has now been widened to make room for a further 14,000 litres of wine while the 37 unearthed bottles will join the family’s collection.

The winery has invested a total of around 250,000 EUR (GBP 215,000) in the “exciting but challenging project”, according to Johannes von Gleichenstein.

Johannes said they have not opened any bottles yet, but he is planning to sample the wine with his family and co-workers at the grand opening of the new cellar in mid-June.

The vineyards of the winery are located on a location named “Hofgarten” which was once owned by Ludwig van Beethoven’s good friend Ignaz von Gleichenstein.