It looks like a picture postcard, but this is a real abandoned location! It's McDermott's Castle in Ireland, hidden away on Lough Key. There's been a castle at the site since the 12th century, although it's been empty for centuries.
The McDermott family lived at the castle until they lost their claim to the island in 1586. Nobody came in to replace them, and nature set about the task of reclaiming the land. Trees and plants now grow through the cracked and broken stonework.