BASEMENTS, basically by definition, are the ugly and unloved stepchildren of any tiered structure.

A damp, dank place to stack cardboard boxes full of ex-lovers' stuff.

A resting place for never-used exercise equipment.

A sunlight-free ecosystem perfect for the cultivation of cobwebs and dust bunnies.

An eminently unsafe hiding place for psychotic clowns armed with blood-stained garden equipment. (Just me?)

But none of these subterranean stereotypes, even the totally rational killer-clown one, apply to what lies beneath the Reading Terminal Market, one of Philadelphia's most recognized historical and culinary contributions.

Directly below that forever-bustling main floor, jammed with produce-perusing locals, wide-eyed tourists, hungry jurors on lunch break and the hundreds of employees who make it all go, is another world - and everything that goes on above would grind to a permanent halt without it.

Come on down

Along the eastern wall of RTM on 11th Street, between Arch and Filbert, you'll find the massive facility's modest loading dock and its perpetually busy polka, whose notes we all know - the crank of pallet jacks, the yells of work-gloved guys heaving and re-heaving, the incessant beeping of heavy trucks thrown into reverse.

It's movie-perfect, a likely candidate for a Rocky jog-through the next time Stallone's geriatric punch machine appears on screen.

Right off this dock sits a pair of unassuming freight elevators, gateway to a vast underground world the average Terminal shopper never even considers.

At roughly 80,000 square feet, or 1.8 acres, the footprint of RTM's basement is identical in size to its more famous sibling up top. They don't look like they're related, but they are.

Dozens of dry storage cages, basically one for each vendor, line one portion of the space. A comparable number of stand-alone refrigerated cases, most of them slapped with the names of the owners written on tape, check in with their electric-hum harmonies. Posted signs, in English, Indonesian and Spanish, break down cleanliness policies. Miles of water, waste and grease pipes kink along the ceiling.

Sections of original brick, still in pristine condition from the market's construction in 1893, sit in silent supportive service. Close to 300 fluorescent bulbs shine down hard on the floor, ensuring that there are no reliable hiding places for murder clowns.

'A true marvel'

Just like up top, the basement is relatively calm in the late afternoon, but from the hours of 4 to 8 a.m. it's a mob scene - vendors and support staff, rushing stuff in and out of their walk-ins, scrambling to prep, trying not to get in each other's way.

It's always been this crazy, but it used to be colder.

In the Market's earliest days, at the turn of the century, the basement "was considered a true marvel" in the field of cold storage, according to David K. O'Neil's book, Reading Terminal Market: An Illustrated History. The entire floor was filled with rooms, some as large at 17,000 cubic feet, cooled by a mechanically operated ammoniated-brine coil and cork insulation system.

Used for food storage and preparation (Bassetts Ice Cream, one of RTM's original tenants, crafted its sweet wares down here until the 1960s), space was also leased out to hospitals for medicine storage and to wealthy epicurean families to stash their perishable snacks.

Yuengling even stored its brewing hops here. "It was, by some accounts, as renowned as the market itself," said RTM general manager Paul Steinke.

"[It] allowed the merchants to carry and keep relatively fresh exotic game meats and produce from around the world," said Carolyn Wyman, a local author who leads the Market's biweekly Taste of Philly Food tours.

But this chill system - so effective an egg stored "for up to fourteen months would still be perfect and could be sold as fresh," according to O'Neil's book - actually cost more to run than the upstairs market.

Over time, the basement, as well as the market above it, fell into disrepair.

Reviving the market

In the early '90s, with the introduction of the Pennsylvania Convention Center, came renewed dedication to RTM as an iconic space and tourist destination. This translated to an ambitious revitalization of the basement level, as well.

When Steinke arrived in his current position, in 2001, the facilities had been improved, but they still didn't compare to what it's like today. "There were some scattered refrigeration units here and there, and all these cages lined up like toy soldiers," he said.

In 2010, when RTM announced an ambitious renovation plan that was completed two years later, more upgrades came to the fore. Pretty much all the storage space, both dry and cold, was moved from the main floor and brought downstairs, allowing six new vendors to open.

A second elevator was installed to accommodate all the newfound up-down traffic. And green initiatives were introduced, such as a system that captures heated water cast off by the fridge units, harnessing its energy to power the market's other hot-water lines.

"Normally, the idea is to just dump it down the drain and waste it," said operations manager Michael Anthony. "Here, we're reusing it."

An elaborate cupboard

The systemic improvements have also spread to market vendors, who either buy and install their own units downstairs or lease existing units and equipment from the market.

Iovine Brothers, the largest-volume vendor in the market, maintains a wildly elaborate series of produce storage down here. Old City Coffee dedicates space to stacking and storing its burlap sacks of green beans, from exotic locales like Sumatra and Brazil.

The Original Turkey, owned by the Bassett family, built a prep kitchen downstairs to roast poultry and make side dishes from scratch. Valley Shepherd Creamery has an enormous fresh-milk tank down here that can be filled directly from the loading dock upstairs, as well as a case for aging cheeses.

Hershel's East Side Deli uses its walk-in to brine its own pastrami and corned beef.

"Even though [the Market] takes up a whole city block, you only have so much space, so you're limited in what you can do," said Hershel's owner Steve Safern. "You really need extra space to make what's upstairs work for you."

All this ticks, along with elaborate facilities management and daily troubleshooting that makes the flow of what goes on up top possible - if it seems to be effortless, now you know better.

"It's like maintaining a whole other market," said Steinke, "except the customers don't ever get to see it."

Drew Lazor has been writing about the local food scene since 2005. His twice-monthly column focuses on unexpected people doing unexpected things in Philadelphia food. If you come across a chef, restaurant, dish or food-related topic that bears investigation, contact him at andrewlazor@gmail.com or on Twitter @drewlazor.