So is it Heritage or Culture? For hundreds of years this was an operational military base and as such it would have had its own culture and life. Soldiers lived and fought here from the 15th Century right up till the First World War. By this stage the castle was less strategically important but was instead used as a store for munitions—hence the "modern" pier.
After this the castle became a monument to the past and after a short time of disuse became a visitor attraction, hence it changed from being part of the community with its military culture to become part of the past, part of our heritage.
If you want to understand today's culture maybe you need to understand the past and where things came from first.