The coins were interpreted as votive offerings related to crossing the Aa. North of the ford some foundation fragments of Kasteel ter Aa (Castle on the Aa) have been made visible. Ter Aa Castle was also more of a manor than a defensible building. In 's-Hertogenbosch Just east of 's-Hertogenbosch, the Aa meets the Maxima Canal. It does not cross the canal, but is led through tubes that run below it. This way, it is not caught up in the flow of the Zuid-Willemsvaart, which is regulated by locks. The Aa then continues under a bridge of the motor way A2. In 's-Hertogenbosch, the Aa is a wide canal that runs straight to the city center. After reaching the city center, the Aa flows along the northern city walls to join the Dommel just west of the Citadel of 's-Hertogenbosch. After that they continue jointly as Dieze. In 's-Hertogenbosch many rowing enthusiasts use the Aa. There are also a lot of recreational boats lying around. Fishermen and swimmers are regularly found on the Aa. On the shore, there are some recreational bicycle lanes with a rather large amount of obstacles to keep out scooters. Inside the city some cultural attractions are situated directly on the Aa. The early seventeenth-century citadel stands out. The city walls east of it are lined with modest housing. Further to the east the Hinthamereinde has the city side of the lunettes of the Muntelbolwerk, and a very decorative nineteenth-century water tower. The Pastoor Bartenbrug is now a rather modest bridge. A previous attempt to (re-)build a bridge at this place was an exceptional engineering failure in 2012-2013. Ecology Along the stretch from Heeswijk Castle to 's-Hertogenbosch the project Dynamisch Beekdal has restored much of the ecological value of the Aa. Environmental processes that were typical for brooks, like shore-erosion, shoal-forming and local fast currents had been eliminated by the canalization. As a consequence, the oxygen content of the water, the shores, and the bottom of the river had decreased in quality. The project restored many of these ecological processes. For marine life, the project created fish ladders in some places where the natural situation could not be restored. This was important because typical brook fishes had decreased and even disappeared, and had been replaced by the european perch and common roach. As a consequence of the project, the ecological diversity of fish in the Aa