Sitting on the Dover strait, Calais is a major port between England and France. Most tourist crossing the channel between the two countries do so via Calais. Since the opening of the Channel Tunnel this has somewhat shifted, but nonetheless, the French end of the tunnel isn't far from Calais anyway, so the place is still busy as ever. Most of Calais was destroyed by bombs during the second World War. Therefore there aren't many historic buildings noteworthy to see. The city is mainly known for its purpose of sifting millions of tourists through its fold every year. Perhaps the most stunning building is the Hotel de Ville with its imposing structure.
Perhaps the most astounding factor about Calais is the cost of property. There are literally many bargains for savvy real estate investors. Some of these range so low they seem near ridiculous. With the range of tourism that passes through the city, it shouldn't be too hard to rent out an investment property most of the year either. Being at the entryway to Britain certainly has its pluses too and would make for some interesting weekends spend abroad.