The Pannonian Limes is a part that is mostly found in Hungary from the Roman front line known as the Danubian Limes, a line of castles and fortifications along the Danube River. The fortification line included guard towers, legionnaires camps (castra) and forts (castella).
The plaques are located in the March 15 square in Budapest where one of the camps stood, describing the relative location of the camps along the Danube which is also drawn on the sidewalk.
The current plaque shows Ad Mures, the Roman name of the fort in Ács-Bumbumkút, Hungary
Notice the two lines representing the Danube River on the upper side of the plaque.
This board is adjacent to another board and above it you can see the route of the Danube River Click for a larger image
In the next photo taken on the same day, part of the line of fortresses was seen, with the route of the Danube River between the various plates Click for a larger image
See the sign attached to this sign Click for sign's details