The lower city, having expanded rapidly during the twentieth century, is the modern centre of Bergamo. At the end of the nineteenth century Città Bassa was composed of Borghi, the residential houses built along the main road that linked Bergamo with the other cities of Lombardy. The main bourgs were Borgo Palazzo along the road to Brescia, Borgo San Leonardo along the road to Milan and Borgo Santa Caterina along the road to Valle Seriana. In the first decades of the twentieth century, the municipality erected major buildings like the new courthouse and various administrative offices in the lower part of Bergamo in order to create a new center of the city. Following that after World War II and during the so called miracolo economico (economic boom) many residential buildings were constructed in the lower part of the city. Of artistic importance in Città Bassa are Pinacoteca dell'Accademia Carrara (picture museum of Carrara academy), known as "Accademia Carrara" and the nearby Galleria d'Arte Moderna e Contemporanea (gallery of modern and contemporary art), known as GAMEC. The lower part of the city is divided into several distinct boroughs: Colognola, Valtesse, Redona, Borgo Palazzo, Celadina, Campagnola, Boccaleone, Longuelo.