Castellum has, through its wholly-owned subsidiary Fastighets AB Corallen, acquired 50% of the shares in CORHEI Fastighets AB. On 13 April 2015, Castellum acquired 50% of the shares in the company then known as Henry Ståhl Fastigheter AB (currently CORHEI Fastighets AB); the current acquisition was of the remaining block of shares. The underlying property value is SEK 2,083 million, and the shares were acquired for SEK 555 million.

Following the transaction, Castellum now owns all of CORHEI Fastighets AB's property stock, consisting of 13 properties in Norrköping and 9 properties in Linköping. The transaction involves 111,480 m2 in Norrköping and 51,024 m2 in Linköping.

Castellum is one of the major listed property companies in Sweden. The value of the properties amount to SEK 42 billion and the properties comprise office/shop and warehouse/industrial premises. The Castellum share is listed on the NASDAQ Stockholm Large Cap list.

Castellum was advised by Mannheimer Swartling in the transaction. The firm's team was led by Hillevi Börjesson and Johan Ljungberg, chiefly assisted by Linnéa Kallhed and Andreas Östman (real estate law).