The experiment took place in 1991, in Brussels, where Roland worked for the Belgium telephone company. Two sets of cesium clocks were located 1.5 km apart. Roland labels them A and B at locations Rue de la Paille ("one battery of the three A clocks") and Rue de Marais ("the other battery of B clocks"). This is enough information for google maps to do the rest of the work.
The street names pinpoint the location to within a city block or two.
That level of detail is sufficient to get a feel for the distance and location:
Google estimate of walking/driving distance from A to B:
A zoom from planet earth to downtown Brussels:
Detail of Rue de la Paille "one battery of the three A clocks" on the South end:
Detail of Rue de Marais "the other battery of B clocks" on the North end:
In the above two end-point photos, it is not known in which buildings the cesium clocks were located. Also note these google screen shots were taken in 2013 and the experiment was performed in 1991. But the purpose here is simply to give a general idea where this experiment took place; details about buildings, floors, rooms and exact cable paths are not important. The maps do confirm the approximate length of the cable runs (1.5 km).