I visited the German Limes and Roman Fort of Saalburg in Bad Homburg in October 2013. The Limes are the only original stone remains still in place today in Germany. The rest was mainly made of wood and therefore only reconstructions can be seen. Having said this, the Roman Fort in Saalburg really gives you a concrete idea of the importance attached to control the borders of the Roman Empire. There are several informative posters in German and English as well as several artefacts excavated from this site. The price is reasonable and parking is free. Hopefully I'll have the opportunity to visit Hadrian's Wall in the near future but I'm glad I visited the German sites first.