The city of Luxembourg is a commune with city status, and the capital of the Grand Duchy of Luxembourg. It stands at the confluence of the Alzette and Pétrusse Rivers in southern Luxembourg. The city contains the Luxembourg Castle, established by the Franks in the Early Middle Ages, around which a settlement developed. Luxembourg City lies at the heart of Western Europe, situated 213 km (132 mi) by road from Brussels, 372 km (231 mi) from Paris, 209 km (130 mi) from Cologne. As of January 2013, the commune of Luxembourg City had a population of 103,641,which was more than three times the population of the country's second most populous commune (Esch-sur-Alzette). The city's metropolitan population, including that of surrounding communes of Hesperange, Sandweiler, Strassen, and Walferdange, was higher than 160,000. In 2011, Luxembourg was ranked as having the second highest GDP in the world, with a per capita GDP (PPP) of $80,119 (US Dollars), with the city having developed into a banking and administrative centre. In the 2011 Mercer worldwide survey of 221 cities, Luxembourg was placed first for personal safety while it was ranked 19th for quality of living. It is a seat of several institutions of the European Union, including the European Court of Justice, the European Court of Auditors, the Secretariat of the European Parliament, the European Investment Bank, the European Investment Fund, and the European Stability Mechanism.