saalburg roman fort with porta praetoria entrance gate, frankfurt, hesse, germany

along ancient archaeology archeological bad borders bridge building castle civilization construction crennelated culture defence defense defensive destination ditch double dry empire entrance europe federal fort fortification fortress frankfurt frontiers gate germania germanic germanicus germany heritage hesse hessen high historic history homburg limes limits main moat mountains museum near part porta praetoria reconstructed reconstruction ridge roman romans saalburg section site state taunus tourist towers travel trench unesco upper wall was watchtowers wehrheim west western windows world