The event was also attended by Environment and Spatial Planning Minister Irena Majcen.
The renovation of the entrance hall and a bridge connecting the entrances into the Gallery of Old Signatures and the Old Cave cost about EUR 3m, which was contributed by the Environment and Spatial Planning Ministry from the concession fees.
In the entrance hall, visitors get ready for entering the cave and get acquainted with the cave rules of behaviour.
The battered thirty-year-old platform from which the train leaves for the cave also received the much-needed refurbishment. The renovation also added a new lighting at the exit of the cave.
The renovated bridge is located at the very spot where a local discovered the interior of the cave 197 years ago.
At yesterday's ceremony, Batagelj&Co. was granted a five-year extension on concession to operate the Postojna Cave and the near-by Predjamski grad, a castle built into a vertical cliff, also a popular tourist destination.
"The extension envisages state investments into the cave, which is owned by the state. I expect our business operations to run normally in the coming years, so we should annually allocate some EUR 1m for concession fees. This puts the state investments at EUR 5m," CEO Marjan Batagelj said.
The planned investments include a renovation of the floor infrastructure at the cave, modernisation of the trains to make them less noisy and a complete refurbishments of the promenade in front of the cave.
Next week a new exhibition pavilion will be opened, while the near-by hotel Jama, which has been closed for the past few years awaiting renovation, should be reopened by Easter next year.
The costs of the renovation of the hotel are estimated at EUR 4m to EUR 5m.
The 2014 business year was very successful for Postojnska jama, as a total of 900,000 people visited the cave or nearby destinations.
Batagelj also told the STA last Friday that the number of visitors this year is already 30% higher than in the same period in 2014. "This means we must be prepared to welcome a larger number of visitors and offer them all they need to be satisfied when they leave Postojnska jama," he added.