The most important thing about this exhibition is something that you are not being told (clearly): It is a large artistic exhibition related to of the idea of the geographical center of Europe. The "official Center of Europe", as set up and commemorated by the Lithuanian government, is a few kilometers away, and free to visit. There is much confusion about this, which the exhibition or the staff doesn't help to clear up.
That being said, it is a large collection of big and small pieces of art in a beautiful forest landscape that will take you about one to two hours to walk around. For most of the pieces, there is very little explanation or context being provided, but some are quite spectacular to see. Only a few pieces come with an interesting explanation of their history. The map and layout of the place is sometimes quite confusing, but you can also look at it as a puzzle to walk around in a nice forest.
The entrance fee is comparatively high for Lithuania, but understandable as this is a private undertaking (apparently) not supported by public money. The restaurant had attentive staff, but limited offers when we visited.
All in all, if the idea of the geographical Center of Europe interests you, you could look at both the "official" site and this park together and see some art, walk through nature and get an artistic interpretation of the history of the idea. Just be aware that the park is quite focused on the artistic aspect, rather expensive and difficult to reach, and the geographical Center of Europe is a matter of interpretation that every place has an interest in calling their own.