Ca 1325, the formerly separate halves of the older walled town were connected (remains of the "penultimate city wall": Laufer Schlagturm, Schuldturm, Weißer Turm, etc.). As the city grew, the older moat was filled in and built over (Weinstadel, Mauthalle, Sieben Zeilen). Construction of the final circumvallation, which doubled the size of the fortified city, began before 1350. By 1425/55, the circuit (ca 5 km) was complete.

At each of the four main gates (Laufer Tor, Frauentor, Spittlertor, Neutor), the inner and outer walls and the open space between them broadend into an enclosed courtyard (Waffenhof) guarded by a massive tower. Of the original 128 towers, more than half survive. When the moat was excavated in the early 15th century, every citizen had either to help with the work or pay a tax. Around 1500, the ramparts were outfitted for artillery and in 1538–45 the castle flank was reinforced with bastions.