The German city of Maanheim is the country's 21st largest city and although one of the lesser known it is still worth a visit. The city is unique amongst German cities in that it has a grid layout city centre and streets are not named but instead each area is given a grid reference. Although there are no flights direct to it, the main hub of Frankfurt is just 40 miles away and regular high speed trains run direct from the city to the airport. Mannheim is an important railwa