I have visited this WHS on multiple occasions before inscription in 2013 and 2015 in Regensburg, Germany, and in 2015, 2017, 2020 in Vienna, Austria. I only had a short video of the archaeological remains of the Danube Limes in Michaelerplatz, Vienna so this time round in 2022 during a brief family reunion, I made it a point to revisit the square and take some photos for my collection.
Not that now I have spectacular photos, nor did I get much more insight by this conscious visit post-inscription. Best time to visit is around noon when the sun shines on the remains. There are a couple of information boards on both sides of the square and also on the floor near the closed off remains themselves. Small appropriately placed bronze plaques give you a better idea of what the foundations once were and their approximate date of construction. As of 2022, there still is no UNESCO WHS plaque for the Historic Centre of Vienna, nor is there one for the Danube Limes.
These kind of WHS detract from the overall value of the WH list and provide no real value added unfortunately. They are a mere tick to bolster capital cities' status or tourist centres as hotspots and are not worth visiting simply for their own merit (should they have any!).