[1] The main building was built in 1300–1585, with major rebuilding especially in 1768 and in 1889 under Hans Jørgen Holm and Gotfred Tvede.

During this period, a number of royal castles were built across the country to strengthen the king's power in the regions and guard against attack.

Completely surrounded by water, it was protected from the open sea although ships of all kinds could sail right up to the island, provided they had crews conversant with the channel to be followed.

Not far to the north and west, there was fertile land where produce could be grown for the castle, with a surplus for the vassal and the king.

Moreover, Nysted Nor was the only suitable site for a building of the kind between Nakskov in the south of Lolland and Stubbekøbing in the northeast of Falster.

However, it is impossible to trace the early history of the castle as there are no written sources and any archaeological evidence is hidden beneath today's building.

For example, in the 1550s, bricks from the Franciscan monastery were used to repair the castle while after the Swedish Wars of 1657-1660, the building had no windows and the towers no roofs.

As time went by, groundfilling works were undertaken and in 1796 a small garden was added on the west side of the castle.

In many cases, however, the vassals appointed a representative to run the castle and its district as they often owned farms elsewhere in the country and were also required to fight in the king's wars.