The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From UIEvolution, Inc.:
Welcome to Detroit, one of the oldest cities in the United States! "Top 25: Detroit", brought to you by the emerging 'Top 25' series by UIEvolution, is an interactive application that allows you the chance to discover, read, and possibly plan a trip around the city of Detroit. With an easy-to-use instant phone call feature, you can quickly call landmarks and begin researching and possibly planning your trip to this great city! And once you visit, you can start bragging to all of your friends and family on where you've been with the easy-to-use Facebook integration!Come discover more about Detroit with Top 25: Detroit!