Only 20 minutes from the center of Bratislava lays one of the most beautiful ruined castles in Slovakia - Devín Castle. It is a personal favourite of mine. Because it is so accessible from Bratislava, a visit to Devín Castle has to be on your Bratislava city-trip itinerary. In 2017, they reopened the Upper Castle, which makes it finally possible to walk around the entire castle grounds. From the Upper Castle, you have an amazing view over the Danube river as well as the Devín village.
Together with Hainburg Castle on the opposite side of the Danube (in Austria), Devín Castle had a defensive function to guard the river entrance to Bratislava. In 1809, the castle was blown to bits by Napoleon, after which it was left in ruin. During the Communist era, the castle took on a far more depressive image, with the area surrounding it being a restricted military zone - in other words, no man’s land between the Easter Bloc and the West, heavily guarded by towers, barbed wire and a shoot-to-kill order in effect. There is a monument just outside the castle area commemorating those that tried to escape to the West but never made it.