I am an underground creature.

Late on this Monday evening in September, Yale University’s campus is a skeleton. Quadrangles, benches, and cobblestone pathways provide the framework for a thriving college campus and yet lie empty of the students that give them daily life. The air hangs in silence. Only I venture through the void. After traversing Cross Campus, I descend a flight of stairs and passed through a glass door.

There, I find the skeleton’s missing flesh: students swarmed around granite tables and leather armchairs. “Are you guys ending up having a party?” “You’re not invited.” “3.1, 3.2, exercise 3.2.” People move in and out of the catacombs beyond. Students seeking a buzz coil into a line in front of a café counter. The smell of espresso wafts through the air, colliding with the scent of chocolate-chip cookies. “Each data has one tenth of concentration.” “I have to read 250 pages and write two pages.” Collages of open Web sites and documents grace laptop screens. Cell phones chime and hum. Cups, backpacks, and books carpet the floor. Two friends stop me for a quick “hello” before rushing off to their subterranean destinations.

Throughout history, countless peoples have sprung up, and a scattered few have ventured underground. Cappadocia, Greece, holds remnants of hundreds of ancient underground villages, a network of passages and communal spaces. Southern Vietnam boasts the remains of the Cu Chi Tunnels, a three-level city including mess halls and a theater that housed hundreds of Viet Cong soldiers. Beneath the bustle of New York City, thousands of “Mole People” find shelter in underground abandoned subway, railroad, and sewage tunnels and live in highly ordered communities. And in New Haven, Connecticut, the underground Anne T. and Robert M. Bass Library, a two-level network with a café, study rooms, couches, and bookshelves, serves as the late-night living quarters for many Yale University students, including me.

During the day, Bass returns to its traditional role as library. Its nighttime inhabitants are elsewhere, blinking in the sunlight. In these hours of daylight, Bass is the place for layovers between flights to aboveground locales. The café hosts tutoring sessions and meetings with Teach for America recruiters. The security gates that divide the café and the inner library remain open. Tourists, businessmen, and prospective students pour in to delight at the bookshelves and examine the studying individuals. Silent students, concentrating on worksheets and computer screens, dot the long wooden tables and brown leather couches of the reading rooms. A thick quiet hangs in the air. Flip-flops and clattering heels provide the only chorus in a hymn of silence.

Individual study rooms, nicknamed “weenie bins,” line the underground corridors, ready for work-related emergencies. In the hours before assignments are due, students banish themselves to solitary confinement. Others self-prescribe weenie bins to rid themselves of the dark bags under their eyes. Once, while seeking a daytime weenie bin, I put my hand on the doorknob of a dark and seemingly vacant cell, only to catch sight of a man, balled into the fetal position, sleeping on the floor. In kindergarten, we had mats for nap time. In college, we have the carpeted floors of weenie bins.

When the patter of feet across Cross Campus’s pathways ceases, the civilization under the sod awakens. The setting of the weekday sun cues the backpack-sporting hordes to begin their descent. The café buzzes, the main avenue of underground social life. Clusters of students discuss everything from pre-gaming to “margins of error I can’t tolerate” and “F times one over G.” One night, a group of girls — one with an orange bean bag taped to her abdomen, another dressed in a garbage bag, a third wrapped in duct tape, and about five others dressed just as eccentrically — bursts into Bass. The girls scatter throughout the café and library, snapping digital photographs, demanding plastic bags, and yelling, “This isn’t the spot!” They continue frantically until they finally scramble back above. It is the evening’s production on Bass’s Broadway.

In these nighttime hours, the inner network of Bass becomes a gated city, shut off from the public eye. Each inhabitant must scan a Yale ID card to enter. The daytime tourists will never know Bass’s nighttime persona. The leather chairs and tables in the main reading rooms — and the corridors and computer clusters that branch out from them — hum with whispers and tapping computer keys. Students play musical chairs among study locales, hopping from wooden tables to leather couches to study booths. One explains his reason for such migrations: varying levels of back support and changing views.

For me, the relocations typically depend on my subject of study: constitutional law calls for an armchair, while ancient Latin lends itself to a table. Other moves take place when I spot a friend. A quick trip over to a companion offers relief from the case law. Muffled conversations revolve around the cute boy who just entered a weenie bin. Lengthy depictions begin with the old “Did I tell you what happened last Saturday night?” Gossip shoots across the reading rooms before you can turn the page. Weenie bin doors are sometimes propped open for guests. Computers flash online chats, connections to the aboveground world. Someone slips on the stairs while returning from the bathroom. Muffled giggles pop up around the room, and a flushed student returns to his seat.

As nighttime bleeds into early morning, Yale’s other major library prepares for its 11:45 p.m. closing, and new streams of students wander through the underground tunnel connecting the two houses of study. As most of New Haven crawls into bed, the library becomes even busier.

At this hour, I need a new diversion, so I stroll through the hidden parts of Bass. Group study rooms are filled with friends scattered about chairs and couches. As I pass, the inhabitants shoot me guilty looks, indicating that their words, muted by the glass windows, likely have little to do with group study. I stumble upon four or five friends. On Bass’s lower level, one friend shows me his online chat with his ex-girlfriend, which he is struggling to complete. His neighbor is struggling to finish her biology homework. They giggle together, each trying to escape the task at hand. As I venture back to my reading room spot, I look at the books gripped in students’ hands around me, which range from Seinfeld Scripts: The First and Second Seasons to A History of Islamic Studies. Some books lie abandoned on sleeping laps. No one wakes the snoring masses: many rely on Bass’s leather chairs for the majority of their rest. Once, one girl allegedly fell asleep and woke up the following morning to discover a blanket covering her.

My eyes continue to scan textbook pages, but at some point my eyelids feel so leaden that I know my time has come to crawl out from underground life. Others have already made the ascent. Many will stay underground until the security guards lock the doors at 1:45 a.m. As I leave the main floor reading room, the café, while no longer serving food, still has signs of problems sets and party-planning. I push through the glass door and mount the stairs. The loneliness of the immobile air returns. The empty benches watch over me as I trudge to my room. The cobblestones welcome my feet. Little do these skeletons know that deep beneath the soot, their flesh resides. Deep in Bass, the heart of Yale University continues to beat.