The factory, whose demise seriously hurt the region around Maribor, has seen a revival in recent years, mostly owing to Chinese-owned bus maker TAM Europe.

The beginnings of TAM date back to 1942, when the Germans used the location on the outskirts of Slovenia's second largest city for the production of aircraft parts for the Luftwaffe.

The authorities in Belgrade decided after the war to turn the site over to vehicle production, naming it in 1947 the Tezno Maribor Car Factory (Tovarna avtomobilov Maribor Tezno).

TAM, whose first vehicles were modelled on Czech designs, quickly became the biggest manufacturer of trucks and buses in Yugoslavia.

In the 1960s the company started exporting substantially, especially to markets of unaligned countries, while it also produced trucks for the Yugoslav army.

In the 1980s, TAM secured the livelihood of more than 8,000 people and in 1986 it produced its 200,000 vehicle; its successor currently has a workforce of 160.

The disintegration of Yugoslavia in the early 1990s entailed a loss of a huge market, which dealt a serious blow to the industrial city, sinking the majority of its big companies, including TAM.

Attempts were made to restructure the state-owned company by dividing it into several smaller ones, but by mid-1996 receivership was launched for all of them.

The separate companies were merged again in 2001 and TVM, the Maribor Vehicles Factory, was established to focus on the manufacturing of buses.

A few years later, TVM, by then a world renowned company, was acquired by Viator & Vektor, which proved another fatal move as the entire Viator logistics empire crumbled during the financial crisis to end in receivership in March 2011.

The broken factory in Maribor, whose quality buses, including for airport use, enabled it to preserve good business ties around the world, was revived in 2014 by Chinese investors. While they mostly focus on airport buses, the aim is to also start producing electric buses as soon as possible.

The hope is that the upgrade will lift the company, named TAM Europe, into the black, as a EUR 5.5m loss on EUR 15.5m in sales revenues was reported for 2016. For a while it seemed as if the new owners might be giving up, but they have recently decided to also buy the production facilities, which they had been renting.

The anniversary was marked in TAM at the end of last week, when the people of Maribor and the factory's former workers were invited to a tour featuring the ongoing production, old models, as well a visit to the industrial zone's mysterious underground tunnels, which have received little public attention so far.

More than 8,500 square metres of tunnels, located 15 metres underground, were dug at TAM during WWII to be able to continue with production amid ever more frequent attacks on the factory.

A 90-minute tour has been organised for one section of the tunnels, which includes a photo exhibition on the creation, rise, bloom and demise of the old factory and a presentation of today's industrial zone.