Many animals have discovered the green islands of Halle (Saale) for themselves. The nutrias or river rats along the Saale are particularly fond of life here: many people come to the riverbank to feed the rodents. As soon as the last night frosts have passed, thousands of toads set off from the island of Peißnitz through the wild Saale to their spawning waters. In the early 1990s, fishermen restocked the Saale with catfish. Here beneath the shadow of the chemical plants of Leuna and Buna, there had been none for 40 years. Now they’re thriving. High above the river reigns the Giebichenstein Castle. In an old dovecote within the castle walls, feral domestic pigeons are helping to advance science. Their eggs are being examined for environmental poisons which the pigeons ingest with their food. In Halle-Neustadt their cousins have “occupied” disused high-rise buildings. Originally cliff-dwellers, these birds love to settle on balconies and niches in the street canyons.