I live in Denmark, and i also live in the city where Kronborg is built, Helsingør, so i pretty much know everything about it. It has been captured by the Swedens and it has been rebuilded many times.
Kronborg acquired its name in 1577 by King Frederick II, but its history goes back to the 1420s, when Erik of Pomerania built the heavily fortified castle called "hook". From here the kings men took advantage of their position by collecting taxes from bypassing ships.
Frederik II's Kronborg:
Frederik II renovated Kronborg from 1574-1584. On top of the outdated castle, he built a magnificent Renaissance castle with towers and he decorated it with columns and sculptures. He was influenced by the European princes, for whom wealth rather than military force had become a symbol of power.
But Kronborg had to live through several dramatic events. On the night of the 25th September 1629 the castle was ravaged by a fire, only the chapel survived. Christian IV rebuilt the palace and made extensive refurbishments and new sculptures in baroque style. In September 1658 Kronborg was bombarded and captured by the Swedes, who took many precious art treasures - including a fantastic ornamental fountain from Frederick II's time.
The Crown work:
In the years that followed they constructed on the outer fortifications, and in 1690 brought Christian V the Crown work as an advanced defense against land attack. From that time the castle werent inhabited by nobles, and in 1785 the military did some rebuilding called Kaserne. Several rooms were rebuilt, but after that the military had left the castle in 1923, it was thoroughly restored and rebuilt as Frederik II and Christian IV's days.
Nowadays its mosly tourists that come to visit Kronborg, but many residents in Helsingør also walk around in there. The castle is free to enter and its very beautiful in there. If you wanna go inside the actual castle, you need to pay 20-30 £. About 200-300 Danish krones. Many people bring their fishpoles, and fish on the beach. But you cant swim, because its to cold, and i also thinks its illegal because of the strong flows (i cant remeber, but im 80% sure). In my opinion, its a great place to come visit!