sentences:  This left the higher and drier ground to the east and south as the only feasible directions for an attack.In the preceding centuries the city had grown beyond its medieval defences, of which only the ruined castle by the river and a stretch of wall that linked the south, east and original north gates, the last known as the inner north gate and now well within the city, still survived.From the south gate to the east gate the wall was high but not thick enough to withstand 17th-century artillery or mining operations.