Budapest later, with the help of the Russian Empire. 1867 was the year of Reconciliation that brought about the birth of Austria-Hungary. This made Budapest the twin capital of a dual monarchy. It was this compromise which opened the second great phase of development in the history of Budapest, lasting until World War I. In 1849 the Chain Bridge linking Buda with Pest was opened as the first permanent bridge across the Danube and in 1873 Buda and Pest were officially merged with the third part, Óbuda (Old Buda), thus creating the new metropolis of Budapest. The dynamic Pest grew into
Budapest terms of the hardiness zone. As per the 1981-2010 climatological norm, widely used in most other European countries, the climate in Budapest has shifted to humid subtropical (Köppen "Cfa"), with averages above 0 °C in the coldest month and above 22 °C in the warmest. Budapest has architecturally noteworthy buildings in a wide range of styles and from distinct time periods, from the ancient times as Roman City of Aquincum in Óbuda (District III), which dates to around 89 AD, to the most modern Palace of Arts, the contemporary arts museum and concert hall. Most buildings in Budapest are relatively