It's rectangular in shape and can carry a six-figure price tag common for some luxury vehicles.

But there's no engine, and the only tires are those that roll across it.

A reserved parking space is a strengthening part of the real estate market in downtown Charleston, providing pricey relief for motorists who might otherwise circle city blocks for on-street parking in some densely populated areas.

On-street parking spaces often are at a premium on the city's narrow streets, which are flanked by historic buildings and homes that were built long before the first automobiles rolled off assembly lines. Some recent sale listings for a single parking space in private parking lots in downtown Charleston have neared $100,000.

Prices vary greatly depending on factors such as proximity to the business district and well-heeled residential enclaves including the French Quarter.

Industry experts say high-price parking space sales are the latest telltale sign of an improving real estate market.

"The parking space increases value," said Elaine Worzala, director of College of Charleston's Carter Real Estate Center. "On a $4 million home, it's not that much money if you think of it that way. A property owner will not have to deal with the hassle of finding parking."

The high-price parking deals are happening in major cities across the country as consumers bring back luxury add-ons shunned during the recent recession and its aftermath.

Manhattan's market made headlines in 2012 when a single parking space in the ritzy Greenwich Village section was listed for $1 million. In Boston, a space to fit two cars in the city's well-heeled Back Bay neighborhood exchanged hands for $560,000 at an IRS auction last year.

In downtown Charleston, prices haven't reached such heights, but tens of thousands of dollars for one space has become a common occurrence.

The local market does not have a detailed database on parking space sales, but anecdotal evidence from several real estate agents suggests a single parking space could fetch as much as $100,000 before the recession sent the market into a tailspin.

Driving deals

Today, there are more scenarios where available parking has helped usher in deals for home and commercial real estate sales.

An example was last year's sale of 25 Calhoun St., a four-story office building near the South Carolina Aquarium.

Patrick Marr, president of CMB Property Co., said the firm's $24 million purchase came after some attention to the area's parking situation.

"One of the reasons we chose the property is the parking (on site) and there's a 1,100-car garage across the street which is not fully utilized and had plenty of spaces, so that was a big help," Marr said.

Parking also is used to help grease the skids on some residential deals downtown.

"It's hard to buy a house for $2 million and not have a place to park the car, that's one driving factor," said Jennifer Davis of Domicile Real Estate Brokerage in downtown Charleston. "Although this is not a factor in some downtown residential areas where there are primarily single-family houses."

Davis is the listing agent for dozens of available parking spaces in the downtown area, each carrying a price tag ranging from $55,000 to $98,000.

The priciest listings Davis has available are roughly a half dozen spaces behind 160 E. Bay St. Those are going for $98,000 each.

The parking lot for about two dozen spaces is book-ended on one side by a row of retail shops and law offices facing East Bay Street. On the other side of the lot is the rear of Prioleau Street, a narrow road that goes past The Harbor Club and a row of condos that face Waterfront Park and Charleston Harbor.

"It brings value to their business or their business expansion or their residence," Davis said, "especially when having parking places downtown is such a rarity."

Davis said she has sold downtown parking spaces to buyers who include home-buyers and business owners.

"Living in a condo or house that does not have off-street parking nearby or is in an areas where on street parking is often occupied proves to be very inconvenient," Davis said.

Some businesses and developers purchase individual spaces or parking lots to satisfy city zoning regulations that cover new building projects or expanding the use of an existing property.

Other buyers include investors who rent the spaces to residents or businesses for a monthly charge.

Downtown homeowners also have the option to pay for a $10 annual parking decal from the city and take a chance on finding street parking.

Home sales

Reserved parking spaces also are growing as a dealmaker for condo and home sales in the historic areas dotted with limited parking.

The parking space is a sizable asset for a homeowner, especially in land-strapped historic areas of the peninsula, Worzala said.

"We are completely constrained and we basically can't go anywhere else but up," she said. "You have to pay a lot of money or decide to move out."

Deborah C. Fisher, owner and broker-in-charge of Handsome Properties, said parking adds immense value to a listing.

Fisher cited the $3.45 million, three-story Georgian townhouse at 78 East Bay St. The 5,271-square-foot home also includes a two-car garage, which she said adds about $250,000 in value to the house, Fisher said.

"It's all about supply and demand," she said. "There aren't that many parking spaces and on certain streets it's good to have a space. ... Anything on East Bay or in the French Quarter, parking is definitely a luxury."

As for businesses, reserved parking adds a layer of convenience for customers, owners say.

Palmetto Carriage Works leases dozens of parking spaces at downtown area parking lots for its customers.

"It's part of my business plan and that's why I do it," said Tom Doyle, owner of the carriage tour company. "Some people offer discounts. For me, I offer discounts if you're walking and free parking if you're not."

Off-street parking also was incorporated into The Cornerstone Apartment Homes, a new complex in the former Kerrison's department store building in the heart of downtown Charleston shopping.

The apartments at the corner of King and Hasell streets include a ramp to the nearby Wentworth Street Garage. Both properties are owned by the Poulnot family.

The apartment tenants are offered a discount of $50 off the regular monthly fee for a parking space.

"I think it's a benefit," said co-owner Gene Poulnot Carpenter. "Everyone has to have a place to put your car."