Cycling Cape Cod’s mostly flat terrain from beach to kettle pond to clam shack, you’d never guess the secret that lies offshore. Just 150 miles out into the Atlantic, ancient volcanic peaks reach (underwater) heights that beat Mount Katahdin in Maine and New Hampshire’s Mount Washington for size; their valleys undulate so deep, they rival the Grand Canyon. These four submarine peaks, or seamounts—Mytilus, Bear, Physalia, and Retriever—are the only such features in Atlantic waters.

This unique marine wilderness is now protected, after President Obama created the Northeast Canyons and Seamounts Marine National Monument this week. The 4,913-square-mile area (about the size of Connecticut) is the first such monument in the Atlantic Ocean and its designation means that fishing, mining, drilling, and other invasive human activities are now and forever verboten.

This area’s dramatic geology is key to its uniqueness: Those peaks and valleys, paired with through-going ocean currents, mean nutrients and oxygen are generously circulated, providing perfect conditions for the the tiny organisms that make up the bottom of the marine food chain. The result is a combined buffet, nursery, and refuge for thousands of ocean creatures, which make it a “critical biological hotspot,” according to a large-scale assessment of the area by scientists from Mystic Aquarium and the New England Aquarium.

So who exactly calls the area home? Forests of seven-foot-tall, brightly colored cold-water “bubblegum corals” that are hundreds of years old and deep-sea fish whose bizarre figures seem to spring from the mind of Miró—or Dr. Seuss. Whales, dolphins, the Greenland shark, and sea turtles cruise above, hunting the prolific schools of whiplash squid, pompom anemone, and fish. Plus, it was recently discovered that Atlantic puffins use the area as their wintering grounds.

Humans will benefit from this protection, too, as some of our favorite fish, like the Atlantic cod, will find a retreat in which to rebuild populations. Sanctuaries are also important to build ecological resilience to stresses wrought by climate change and provide a kind of undisturbed “control” or reference area for marine scientists to study.

This new monument is the latest in a series of bold conservation moves by President Obama: He has now set aside more land and water than any previous commander-in-chief, and it follows on the heels of Maine’s Katahdin Woods and Waters National Monument, NYC’s Stonewall Inn, and a quadrupling of the Papahanaumokuakea Marine National Monument in Hawaii.

Before the announcement, all four existing American marine monuments were in the Pacific. Now the Atlantic, which covers one-fifth of the earth’s surface, gets some love too.