Lithuanian litas
Between the World Wars industry prospered in Kaunas; it was then the largest city in Lithuania. Under the direction of the mayor Jonas Vileišis (1921–1931) Kaunas grew rapidly and was extensively modernised. A water and waste water system, costing more than 15 million Lithuanian litas, was put in place, the city expanded from , more than 2,500 buildings were built, plus three modern bridges over the Neris and Nemunas rivers. All the city's streets were paved, horse-drawn transportation was replaced with modern bus lines, new suburbs were planned and built (Žaliakalnis neighbourhood in particular), and new parks and squares were established. The foundations of a social security system were laid, three new schools were built, and new public libraries, including the Vincas Kudirka library, were established. J. Vileišis maintained many contacts in other European cities, and as a result Kaunas was an active participant in European urban life.