Some of Sci Fi’s most interesting aliens look like or share traits with Earth’s arthropods. Arthropods include insects (like, ants), centipedes and millipedes, arachnids (like, spiders) and crustaceans (like, crabs and lobsters). Think of the giant sandworms of Arrakis in Dune, the spider-like buggers of Ender’s Game, and the Bugs of Starship Troopers, which are very cool alien space bugs. All of these aliens are human-size or larger.
But on Earth, physics and genetic history have kept arthropods much smaller than humans. The largest arthropods alive are certain crabs and lobsters, and even the largest of these, the American Lobster, does not grow to 50 pounds. Yes, that’s big for a lobster, but not exactly the match of a human in a gladiator ring or in a space battle. It’s certainly not large enough to develop the large, complex brain needed for sentience.
On Earth, arthropods developed exoskeletons (skeletons on their outsides), which provide great protection from enemies and allow the evolution of an amazing range of weapons and tools. Consider the giant claws of a crab or the sting of a scorpion. But exoskeletons restrict how large arthropods can afford to grow. Molting — the process of replacing an exoskeleton as the animal grows — takes longer the larger the animal grows. Some crabs take an entire month to climb out of their old skeleton and allow the new one to harden up. Exoskeletal legs are also basically tubes filled with muscle and tissue. If an arthropod grew to human size, the exoskeleton would not be strong enough to hold up the ‘pod’s weight. And the arthropod’s muscles would not be strong enough to move the exoskeleton around.
Arthropods also evolved in a way that their cells get oxygen through gills, their skin, or tubes in their bodies, called tracheae, that open directly to the outside air. Humans and other vertebrates have lungs and feed oxygen to the cells through the blood. As ‘pods grow larger, it becomes harder and harder to get enough oxygen through their skin or tracheae to every cell. A ‘pod as large as a human might easily suffocate.
As ‘pods grow larger, it becomes harder and harder to get enough oxygen to every cell.
But a ‘pod-like animal that evolved on another planet might not have those limits. For example, we can imagine an alien “Pod” that evolved from simpler ancestors with both an internal and external skeleton. Such creatures might have an internal skeleton in their arms and legs to support the weight of a large body. But with a partial exoskeleton, the Pod might have a natural helmet for its head, giant claws, or possibly a scorpionlike tail. With lungs instead of tracheae, the Pods could breathe like we do. Finally, on an alien world with different elements in the rocks and soil, the Pods might evolve with exoskeletons made from lighter, stronger materials that would allow them to grow mighty armor and still move quickly.
Today, I want to focus on cities built beneath the ground. One is a fortress built beneath the frozen crust of a distant planet, and the other is a secret, centuries-old city far beneath New York City.
In Fortuna by Kristyn Merbeth, Corvus is a soldier on the planet Titan, a frozen planet divided by an eternal civil war. Because of the severe cold and the constant fighting, Titans live in caves and in cities built beneath the ground.
In Chapter 18, Corvus is leaving the military and taking a train from Fort Sketa to a fortress city filled with civilians.
“The next morning, I wake early to head to the train for the sake of avoiding unwanted company. The station is just below the surface, chillier than the lower levels of the building, and the ceiling trembles under the weight of activity in the hangar above.
. . . . “When I first arrived on Titan, underground rooms made me feel caged and nervous. Especially so in places like this, where the ceiling occasionally shakes loose clouds of dust, and the rumble of trains along the tracks makes it feel like the whole building could collapse on top of me. Over the years it’s become normal. Now, for the first time in a long time, I wonder if it will feel strange to walk in the sunlight again.
. . . . “The underground fortress of Drev Dravaask is beautiful. It’s warm enough that I take off my outer coat, and not overcrowded with people and buildings like the major cities of other planets. There is a simple elegance to its architecture and a surprising kindness in its people. They all nod or smile at me as I pass, or press their fingers to their hearts if they notice the [military] brand on my wrist. I return the gesture without thought, drinking in the quiet. It’s so peaceful here compared to the rest of Titan. Neither the storms nor the war can touch this place.
There is a simple elegance to its architecture and a surprising kindness in its people.
“Drev Dravaask has held its ground for over a century while cities around it crumbled. The stability allows people to build lives here that do not revolve around war. There are restaurants and shops, bars and inns, families that aren’t missing pieces. Of course, there is also a huge military recruitment center near the heart of the city, and posters advertising the perks of service on every street corner, so it is not possible to forget entirely.”
Sister Scorpia sees Drev Dravaask, the undground city on Titan, very differently
Corvus was born on the planet Titan and returned as an adult to serve his mandatory three-year tour as a soldier in Titan’s eternal civil war. His sister, Scorpia, was born on the family’s spaceship, Fortuna, and has a very different impression of the underground Drev Dravaask. After storing Fortuna in a cave hangar on the surface, Scorpia and her family take a slow, rusty elevator deep into the planet.
“The city of Drev Dravaask is carved into the earth beneath the surface of Titan, dark and damp caves forming homes and businesses and more. The surface of the planet is too cold, too stormy; water freezes up there; and plants won’t grow, and people die slowly and numbly without realizing that they’re dying. Down here, close to the hot springs that run beneath the surface, it’s a handful of degrees warmer.
“It would be easy to be miserable in a city like this, but the people of Drev Dravaask find pockets of happiness in their cold underground world. As we head inward, a trio of soldiers sways past us arm in arm, belting a severely out-of-tune version of Titan’s planetary anthem. A cluster of children giggle in an alleyway, finger-painting dirty words on the walls. A hunched street vendor with a face full of battle scars hands a carefully wrapped meal to a gaunt teenager on the street corner.”
Gregor the Overlander finds a magical city of humans buried deep underground
In Gregor the Overlander by Suzanne Collins, Gregor and his baby sister, Boots, discover a mysterious land, called the Underland, filled with giant, talking rats, bats and cockroaches, that lies far beneath New York City.
Gregor stumbles into the Underland and finds a city hidden deep beneath New York City
“There are but five known gateways to the Underland,” said Vikus. “Two lead to the Dead Land, but you would never have survived those. Two gateways open into the Waterway, but your clothing is quite dry. You are alive, you are dry, from this I surmise you have fallen through the fifth gateway, the mouth of which I know to be in New York City.”
Vikus, a mysterious, bearded man with silver hair and violet eyes, leads Gregor to the human capital of the Underland.
“He followed Vikus down a tunnel lined with stone torches to a small arch filled with something dark and fluttery. Gregor thought it might be more bats, but on closer inspection he saw it was a cloud of tiny black moths. Was this what he had passed through when he stumbled into the stadium?
“Vikus gently slid his hand into the insects. ‘These moths are a warning system peculiar to the Underland, I believe. The moment their pattern of flight is disturbed by an intruder, every bat in the area discerns it. I find it so perfect in its simplicity,’ he said. Then he vanished into the moths.”
Welcome to the city of Regalia!
“Behind the curtain of wings, Gregor could hear his voice beckoning. ‘Gregor the Overlander, welcome to the city of Regalia!’
. . . .
“Gregor didn’t know what he’d expected. Maybe stone houses, maybe caves—something primitive. But there was nothing primitive about the magnificent city that spread before him.
“They stood on the edge of a valley filled with the most beautiful buildings he’d ever seen. New York was known for its architecture, the elegant brownstones, the towering skyscrapers, the grand museums. But compared with Regalia, it looked unplanned, like a place where someone had lined up a bunch of oddly shaped boxes in rows.
“The buildings here were all a lovely misty gray, which gave them a dreamlike quality. They seemed to rise directly out of the rock as if they had been grown, not made by human hands. Maybe they weren’t as tall as the skyscrapers Gregor knew by name, but they towered high above his head, some at least thirty stories and finished in artful peaks and turrets. Thousands of torches were placed strategically so that a soft, dusky light illuminated the entire city.
“And the carvings . . . Gregor had seen cherubs and gargoyles on buildings before, but the walls of Regalia crawled with life. People and cockroaches and fish and creatures Gregor had no name for fought and feasted and danced on every conceivable inch of space.”
Your favorite underground cities
Sci fi has lots more underground cities. Which ones are your favorites? Were they built on Earth, on other planets, or in other universes? Were they built by humans, alien life, or ancient creatures long gone?