Particularly desirable as a building material were the limestone-like limescale accretions from the inside of the aqueduct. In the course of operation of the aqueduct, many sections had a layer as thick as . The material had a consistency similar to brown marble and was easily removable from the aqueduct. Upon polishing, it showed veins, and it could also be used like a stone board when cut flat. This artificial stone found use throughout the Rhineland and was very popular for columns, window frames, and even altars. Use of "Eifel marble" can be seen as far east as Paderborn and Hildesheim, where it was used in the cathedrals. Roskilde Cathedral in Denmark is the northernmost location of its use, where several gravestones are made of it. Medieval legend held that the aqueduct was an underground passage from Trier to Cologne. According to the legend, the Devil had bet the architect of the Cologne cathedral that he could build this tunnel faster than the cathedral could be erected. The architect took the bet and drove the men to work with great haste. One day, the construction workers broke into the aqueduct, where flowing water could be seen. The Devil's giggling is said to have driven the architect to suicide by jumping from the half-finished cathedral tower. Supposedly, the architect's death (and not the lack of funds) was the cause of the centuries-long delay in the completion of the construction. A few medieval writings on the aqueduct lost sight completely of the original purpose of the construction. Some say that it carried not water, but wine to the city, for example, the Gesta Treverorum written from the 12th century, and the Hymn to Saint Anno of the 11th century. Tourism The Römerkanal-Wanderweg ("Roman canal hiking trail") runs for approximately along the aqueduct's path from Nettersheim all the way to Cologne. Public transport links are good, allowing the trail to be walked in various stages. It may also be used as a bike trail. There are approximately 75 information stations along the way, providing an excellent view of the aqueduct. Legacy Archaeological research on the Eifel aqueduct started in the 19th century. C.A. Eick was the discoverer of the farthest source from Cologne at Grüner Pütz near Nettersheim (in 1867). Systematic study of the aqueduct was carried out from 1940 to 1970 by Waldemar Haberey (de). His 1971 book is still a suitable