Seefeld's widow, Sophie Bille, carried the project forward. By 1606 the main building was complete in the sense that mattered — habitable, imposing, and three-sided. Whether the decision to abandon the fourth wing was financial or simply practical, nobody recorded, but it was made, and those two half-timbered gables at the rear are its visible edge. There is something disarming about it. Most great houses bury their compromises behind a symmetrical façade; this one has been showing hers since the reign of Christian IV. The castle occupies twenty hectares on a rectangular bank west of a meadow that was open seabed when the water still reached this far inland; another 239.8 hectares of farm and woodland make up the surrounding estate, with the farm buildings and workers' quarters ranged to the west.

There was something here long before the brick. King Christopher II is thought to have owned a farm on the site, which he pawned in 1327 under the name Svorttorp — pawning property being, in Christopher's case, less an emergency measure than a style of government. The estate enters the written record properly in 1388, when Jens Lagesen Udsen is named as owner in a parchment letter that is still kept in Sostrup's own vault. Six hundred and thirty-odd years later, the document and the building it describes are in the same place, which is not a thing that happens often.

Sostrup has twice been renamed by its owners' ambitions. In 1725 it became the manor house of the County of Scheel and took the county's name, which it carried until the county was wound up in 1823. In 1829 Jacob von Benzon acquired it and converted it into an entailed estate called Benzon — a legal device designed to hold land in one family forever, which in practice it rarely managed. Only in 1944 did the house go back to being Sostrup. The owners in between read like a directory of the Danish nobility: Udsen, Kaas, Munk, Hvas, Seefeld, Skeel, Benzon, Mylius, with the Danish state stepping in twice when things went wrong.

The strangest chapter is also among the most recent. From 1961 until 2013, Sostrup was a convent, run by Cistercian nuns of the Catholic Church, who used the castle for retreat and boarding and built a church to the south-west of it. A Renaissance manor raised by Lutheran nobility in a Lutheran kingdom spent fifty-two years as a Catholic religious house — and it left physical traces, chief among them the plain cells the sisters slept in. Those cells are the reason the building's current life is possible at all.

Sostrup was sold on 1 June 2014 to a sister and brother, Kirsten and Anders Bundgaard, who restored it and opened it to the public on 22 August 2015 as a venue: a restaurant, rooms for gatherings of anywhere from thirty to three hundred people, guest accommodation, and twenty-five of the old monastery cells available by the night. Kirsten B. Swift held the castle alone from 2015 until 2024; since 2025 the owner has been Thomas Kirk Kristiansen. You can now book a bed in a nun's cell inside a nobleman's unfinished courtyard, eat dinner in a Renaissance hall, and walk out of the back door to find two half-timbered gables still waiting for the wing that was cancelled in 1606.