Around 14 June, the circumvallation was in principle finished. Due to difficult terrain large gaps remained, which was not seen as a problem as the structure served no real function. In 1632, Frederick Henry's circumvallation had been much more extensive. The same day a third bridge was completed to the south of the city. On 16 June, gun batteries were positioned, two in front of the Tongeren Gate and one on the north slope of the St Pietersberg which offers an ideal vantage point over the fortress. The guns, once in place, immediately opened fire, spending three thousand shot in the first six hours. It now became clear that the Tongeren Gate was the main object. It formed a weak point in the defences as it was protected by a small ravelin only and the city wall behind this was still mediaeval in form, without a full height backing earthwork, though a cavalier was present, the Tongerse Kat. Furthermore, there was only a dry moat to its north. In front of the ravelin a new lunette had been constructed but to obtain the necessary earth, to the south a nearby redoubt protecting the Jeker sluice inlet had been levelled. Vauban later criticised this, claiming that if the redoubt had still be present he had not dared to attack at this point because of its enfilading fire. Such fire was still provided by a large protruding hornwork to the north of the gate and the Groene Halve Maan, a demi-lune to its south.