The website Insider Monkey says "French Colonial is the architectural style that is common across Vietnam. It is also reflected in the government buildings in Hanoi, including the Presidential Palace, which was completed in 1906 and Hanoi Opera House". The ranking was made based on analysis and data released by various websites that cover travel and architecture. They included Conde Nast Traveler article "The world’s 20 best cities for architecture lovers, Travel Channel’s world’s top architecture cities", and "10 cities for architectural enthusiasts" by Suitcase Magazine, among others. Countries were ranked based on the number of times their cities were listed in the above-mentioned sources./.