"Those who pass have always passed," reads the graffiti on the light blue doors leading to the abandoned cyclotron on the first floor of Pupin Hall.

The only ways to access the floor's main hallway are either to make it through two locked doors or to climb over the heating element in an antique bathroom across from the building's elevator. This level, where Nobel laureates Enrico Fermi and Isidor Isaac Rabi once worked, was home to the Manhattan Project.

Upon entering, visitors are confronted by a hallway strewn with dusty chairs, dangling wires, and knocked-over filing cabinets. A former hub for adventure-seekers because of the array of documents and potentially dangerous scientific materials lying around, the floor was cleared out by the University in 2003.

But while the radioactive samples and old hiring records are gone now, there is still a large collection of strange items inexplicably present in the basement of a physics lab. In one room are tables covered with binders of scientific data, decades-old scientific journals, boxes of Phillies Blunt cigars, and a model-train-making catalogue. In a room two doors down is a device that could once split an atom, a vacuum chamber capable of producing extraordinarily low pressures, and a bank of 60-year-old NASA computers.

Most of the walls are now covered in graffiti, some decades old. Many of the tags are the work of seasoned Columbia explorers and vandals, a network of "tunnelers" who have spent their time penetrating the bowels of Columbia's expansive tunnel system.

One such tunneler, who identifies himself in graffiti only as Benoit, SEAS '01, has tagged virtually every room on the first floor of Pupin, as well as in other seldom-visited underground areas of Columbia.

"The first floor was used regularly up until the late sixties, when it was essentially abandoned. ... From then until Summer 2003, it was used as a storage house for old papers, books, physics gadgets, and records about people who were employed in Pupin from 1942 to the early seventies," Benoit wrote in an e-mail sent from an address included with many of his tags. "One could spend days looking through things there-I personally have a CU Security Guard's ID dated from 1946, and papers dating back to the late 1920's, as an example."

Benoit said he disproved the urban legend that gamma ray emissions remain from the old cyclotron, after he and a friend surveyed the floor with a Geiger counter. According to Benoit, "no radiation out of the ordinary was found."

Although tunnelers rarely do more damage than graffiti, some students have been more destructive in the past. Ken Hechtman, a founding member of the Allied Destructive Hackers of Columbia, was asked to withdraw from Columbia after stealing a partially depleted sample of Uranium-238.

Andrew Millis, professor and chair of the physics department, said in an e-mail that the department would like to convert the Pupin basement into laboratory space.

"The cost would not be small," he wrote. "It is in many senses prime experimental space. Because it is low down and on bedrock you can put vibration-sensitive experiments there, which would otherwise be impacted by the torsion and bending modes of the building."