It’s tempting to think that North American beavers are destructive. They strip bark from trees when they’re not gnawing them down entirely, and build lodges on waterways that seem to block the natural flow. But wildlife research indicates that everything native beavers do is a net benefit to the local environment. That’s one of the goals of International Beaver Day today: To let people know that the dams built by “nature’s engineers” create vital habitat for wildlife, and by slowing the flow of waterways, they prevent flooding.

It’s tempting to think that North American beavers are destructive. They strip bark from trees when they’re not gnawing them down entirely, and build lodges on waterways that seem to block the natural flow. But wildlife research indicates that everything native beavers do is a net benefit to the local environment. That’s one of the goals of International Beaver Day today: To let people know that the dams built by “nature’s engineers” create vital habitat for wildlife, and by slowing the flow of waterways, they prevent flooding.

Pope Clement VII commissioned the construction of Pozzo di San Patrizio (Saint Patrick’s Well) in Orvieto, Italy, during the early 16th century. The pope was hiding out in the Umbrian fortified city after the 1527 sack of Rome. His motivation was to store water in the event of a siege on Orvieto.

The double-helix stairwells lining the walls of the well allowed water-bearing donkeys to descend and ascend without getting in each other’s way. Today, the well is one of many examples of Renaissance engineering that still stand.

Pope Clement VII commissioned the construction of Pozzo di San Patrizio (Saint Patrick’s Well) in Orvieto, Italy, during the early 16th century. The pope was hiding out in the Umbrian fortified city after the 1527 sack of Rome. His motivation was to store water in the event of a siege on Orvieto. The double-helix stairwells lining the walls of the well allowed water-bearing donkeys to descend and ascend without getting in each other’s way. Today, the well is one of many examples of Renaissance engineering that still stand.

Visit the vibrant rainforests of Niah National Park on the Malaysian side of Borneo and you’ll see a whole lot of leaves like this one. The island’s tropical climate supports one of the most diverse ecosystems in the world, and the range of flora and fauna here can be staggering. The national park is named for the Niah Caves, which include one of the largest known caves in the world. The Great Cave of Niah is a gold mine for biologists interested in unusual insects and the immense population of bats that call the cave home.

Visit the vibrant rainforests of Niah National Park on the Malaysian side of Borneo and you’ll see a whole lot of leaves like this one. The island’s tropical climate supports one of the most diverse ecosystems in the world, and the range of flora and fauna here can be staggering. The national park is named for the Niah Caves, which include one of the largest known caves in the world. The Great Cave of Niah is a gold mine for biologists interested in unusual insects and the immense population of bats that call the cave home.

The restored buildings of a former monastery sit atop waterfalls near the entrance to Saint Beatus Caves. Saint Beatus of Lungern arrived at the hills above Beatenberg, in what is now Switzerland, sometime in the late 1st century AD. It’s said that in the caves behind the waterfall, he defeated the dragon that lived there and set up his hermitage.

The legend of Beatus isn’t clear on his birthplace. He’s either Scottish or Irish, and probably a pastiche of other, more easily documented saints. In any case, Saint Beatus is now the namesake for both the monastery and the caves.

The restored buildings of a former monastery sit atop waterfalls near the entrance to Saint Beatus Caves. Saint Beatus of Lungern arrived at the hills above Beatenberg, in what is now Switzerland, sometime in the late 1st century AD. It’s said that in the caves behind the waterfall, he defeated the dragon that lived there and set up his hermitage. The legend of Beatus isn’t clear on his birthplace. He’s either Scottish or Irish, and probably a pastiche of other, more easily documented saints. In any case, Saint Beatus is now the namesake for both the monastery and the caves.

Giant salvinia is a floating fern native to Brazil, where it’s kept in check by competition from other plants and by a weevil that loves to feast on the buoyant fronds. Exportation for aquarium use has brought giant salvinia to the United States, where it’s a highly invasive plant that can quickly cover a pond or lake, and shut off light and oxygen from aquatic life.

Giant salvinia is a floating fern native to Brazil, where it’s kept in check by competition from other plants and by a weevil that loves to feast on the buoyant fronds. Exportation for aquarium use has brought giant salvinia to the United States, where it’s a highly invasive plant that can quickly cover a pond or lake, and shut off light and oxygen from aquatic life.