New Slains Castle, to distinguish it from nearby Old Slains Castle, was originally a 16th-century tower house, built by the 9th Earl of Erroll. The wings around the courtyard were extended in 1664 by addition of a gallery or corridor, and in 1707 the entrance front was renewed.
In the 1830s the 18th Earl commissioned the Aberdeen architect John Smith to remodel the castle. This resulted in a virtual rebuilding of Slains in a Scots Baronial style, including granite facings, in 1836–1837. Gardens were laid out in the late 1890s.
At first inspection the ruin appears to be a blend of several different architectural styles and periods, due to diverse masonry including older mortared granite, mortared medieval red brick, mortared sandstone and newer well faced granite. In fact most of the architecture seems to derive from a rather cohesive interval 1597 to 1664, which construction is the most expansive and includes the mortared rough granite and medieval brick. The 1836 work adds smoother granite facing that contrasts with the older construction style.
The defensive works of the castle include use of the North Sea cliffs; an abyss to the west that functions as a deep impassable moat; and a ruined rampart that would have been the main entrance on the south. The ruins include reasonably well preserved elements of three- and four-storey structural elements and a basement course over some of the range, especially at the eastern side. There are well-preserved basement kitchen works with numerous firepits and masonry indented storage spaces. The internal doorways are primarily of well-preserved wooden lintel construction, with numerous examples of mortared sandstone and medieval brickwork archways. The interior of the ground level is a maze of passageways and smaller rooms, reflecting a high state of occupancy in 17th-century times.
References:Kakesbeck is one of the largest medieval fortifications in Münsterland and the oldest castle in Lüdinghausen. The imposingly grown complex originated in 1120 as a motte, a small hilltop tower castle. After numerous changes of ownership, the castle was extended onto two islands, but it was not until the 14th century that it underwent significant alterations and extensions under the von Oer family. The estate experienced its heyday in the middle of the 18th century, when it covered an area of almost one square kilometre and consisted of five further outer castles in addition to the core castle, which were secured by ramparts and moats.
The well-maintained condition of the castle today is thanks to the late Wilfried Grewing, the former lord of the castle. The foundation named after him has been particularly committed to preserving the property since 2020.