With their grand architecture, castles are some of the world's most scenic, postcard-worthy sights. But these already-majestic structures are elevated to "fairy tale" status when perched on mountaintops or cliff edges. Although these castles set on precarious sites offer spectacular views, their locations were crucial for castle builders for another reason. "Castles were planted in the best place to control road and river routes," Marc Morris, a historian and presenter of the UK television series Castle, told weather.com. "Sometimes this...