role has also been filled by the Siemens-Schuckert Orenstein & Koppel cars, delaying their retirement. Though Line A ran on a different voltage to the rest of the network, it was converted to the 1500 V used on the rest of the network when the 200 Series trains began to arrive. On the other hand, Line B has traditionally been the most troublesome of the network given its different voltage and the fact that it uses third rail electrification as opposed to the overhead lines used on the rest of the network, making it in effect a separate entity not capable of sharing its stock with other lines. Presently this line uses 1950s rolling stock acquired from Tokyo's Eidan 300/400/500/900 series Marunouchi Line, along with CAF 5000 and CAF 6000 stock acquired from Madrid which are to replace the aging Eidan stock. The line, along with its remaining third rail stock, is being converted to overhead lines at 1500 V, after which the entire network will be standardised. Culture and heritage The Buenos Aires Underground has historically been characterised by murals and other artistic works in its stations, making it a kind of museum throughout the system. These works, and a number of complete stations, are considered part of the cultural heritage of the city and several of them were declared National Historic Landmarks in 1997. National patrimony Line A is renowned for having kept its original 1913 rolling stock running on the line up until 2013, making them the oldest underground carriages in commercial service in the world at the time. They were built by La Brugeoise, et Nicaise et Delcuve, a Belgian rolling stock manufacturer established in the city of Bruges, between 1913 and 1919. Entirely made of wood, they were originally designed to run as underground as well as tramway cars, but they were adapted in 1927 to their current style for underground service only. In March 2013, La Brugeoise subway carriages were replaced by new Chinese 200 Series rolling stock, just 11 months prior to their 100-year anniversary on the line. The original rolling stock has since been maintained, some in exhibition and some being converted to 1500 V to run tourist services on the line. During the festivities of the 100-year anniversary of the underground on 1 December 2013, many restored La Brugeoise trains circulated Line A and there was a symphonic orchestra at Plaza