Budapest is the capital city of Hungary formed by the unification of Buda, Pest, and Óbuda in 1873. It has over 1.7 million residents within its 525 square kilometers and is situated along the Danube River. Budapest has a long history dating back to Roman settlements and was an important focal point during the Hungarian Revolution of 1848 and Revolution of 1956. Major landmarks include Buda Castle, Matthias Church, Heroes' Square, Fisherman's Bastion, and the Hungarian National Museum. The city is also known for its thermal baths and spas dating back to Roman times and has several islands along the Danube such as Margaret Island and Csepel Island.