Prince-Archbishop Leonhard von Keutschach further expanded the fortress during his term from 1495 until 1519. His coadjutor Matthäus Lang von Wellenburg, who was later to succeed Leonhard, in 1515 wrote a description of the Reisszug, a very early and primitive funicular railway that provided freight access to the upper courtyard of the fortress. The line still exists, albeit in updated form, and is probably the oldest operational railway in the world. The current external bastions, begun in the 16th century and completed in the 17th, were added as a precaution because of fears of Turkish Invasion.