When you visit a neighbor and put your cursor over a culture building or trader you get a text with its name and level. I heard that culture buildings are not going to get any upgrades so I assume this is a bug.
At the moment, it is not yet known whether or not upgrades will become available for Cultural Buildings in the future. For now all cultural buildings are level 1 and therefore it's not really a bug, so I'll set this topic to "not a bug".
There's nothing known about whether or not there will be upgrades for cultural buildings in the future at this moment so we'll have to wait for any news on that. However, it is strange that there is a difference between your own city view and you neighbours city view, so thank you for pointing this out. We will ask the developers about that, so I changed the topic to "Confirmed".