Standing deep in the German countryside for over 500 years, Heidelberg Castle was once home to the country's first university and is now part of the surrounding ecosystem. From toads swimming in the grounds' fountains to peregrine falcons nesting in the bell tower, tour a medieval mausoleum steeped in nature.

North of the Pyrenees stands the ancient Carcassonne, a stone fortress that's faced sieges, endured the brutality of the Spanish Inquisition, and thrived as a center of wealth during the salt trade a millennia ago. Today, it's a protected sanctuary and an avian paradise for robust avocets, exotic flamingos, and more.

Predjama Castle is carved into the heart of a Slovenian mountain and nestled among stunning natural attractions, including the eerie Postojna Caves and Lake Cerknica--Europe's largest intermittent lake. Brown bears, aquatic salamanders known as olms, and more thrive in the shadow of this imposing fortress.

In the sun-baked plains of southern Spain, between Europe's only desert and the mighty Sierra Nevada, lies Alahambra, a magnificent Moorish palace of lush gardens and shimmering fountains. Join us on a sweeping tour of the wildlife within, including Iberian frogs, white-bellied hedgehogs, and more.

The landscape surrounding Neuschwanstein Castle is famous for its rugged peaks, deep gorges, and river valleys packed with wildlife. Alpine ibex are at home on the surrounding tricky slopes, while golden eagles patrol the skies above. Embark on a rich journey through the human and natural history of these medieval grounds.