Complex sentence: On 6 October 2011 Aberdeen City Council voted to demolish St Nicholas House their previous headquarters and put the site on market afterwards this is due to the completion of the refurbishment of Marischal College earlier in 2011 which is now the Aberdeen City Councils New headquarters.
Split into simpler sentences: On 6 October 2011 Aberdeen City Council voted to demolish St Nicholas House, their previous headquarters, and put the site on market afterwards. This was due to the completion of the refurbishment of Marischal College earlier in 2011 which is now the Aberdeen City Council's new headquarters.