The Bensberg subway station is a 3-minute walk away.
From there, the journey by direct train to Cologne city center takes only 30 minutes.

For your travel planning you can look into three possible airports:

Cologne Bonn Airport – approx. 20-minute drive by taxi to Schloss Bensberg
Düsseldorf Airport – approx. 60-minute drive by taxi to Schloss Bensberg
Frankfurt Airport – approx. 1h 50-minute drive by taxi or 1h 40min by public transport to Schloss Bensberg
(train to Cologne Messe Deutz and then subway to Bensberg)