Arriving in the 1st century AD, Celtic tribes were first to build on the city’s present-day location.  They were followed by Romans who built a town called Aquincum.  Towards the end of the 9th century the region was occupied by Magyar tribes who had migrated westward from the Ural Mountains.  Founded by Hungarian King Béla IV after the Mongol Invasion (1241-1242), Buda expanded with the addition of Gothic-style houses, cobblestone streets, and a royal palace positioned on a hill above the Danube.  Beginning in the late 18th century, Pest’s population grew rapidly as it evolved into the nation’s administrative and economic center.  Buda was conquered several times by Ottomans who occupied the city for 150 years and built public structures including the Rudas Baths.  A multinational Christian army reconquered the city in 1686.  In 1867 Hungry became part of the Austro-Hungarian Empire under a single monarch and six years later Buda and Pest, along with Obuda (Old Buda), merged to form the city of Budapest.  The 20th century brought watershed events such as a 1956 demonstration against the communist regime that was met with a show of force by Soviet tanks.  Hungary finally received its independence in 1989 and soon after, multiparty elections were held.  The last Soviet troops withdrew in 1991.