Downtown Easton has the elegant State Theatre, once an eyesore, now a premier Lehigh Valley concert hall. In Bethlehem sits the sturdy Radisson Hotel Bethlehem. Not long ago, it was on the fast track to blight. But it was saved by investors who kept the old inn alive. Allentown has an aged theater and a unique, Roaring '20s-era hotel on the same block. But the theater is in ruins. The hotel is shuttered. One man is behind Allentown's nightmare: Mark Mendelson.

A family trust and a business Mendelson runs own the foul, blighted Colonial Theater and the vacant, lifeless Americus Center Hotel, declared this summer unfit for human habitation.

Another Mendelson business owns other property nearby, a parking lot that once was the doomed Corporate Plaza office building, and the trust owns the squalid Sal's Spaghetti House, which was a thriving restaurant when he bought it in 1986.

A downtown bank branch that a second Mendelson trust owned last month went to sheriff's sale, where it was bought by his son. That building has stood empty for three years.

For most of the 17 years since he came to town, the brash 46-year-old businessman has maintained a simmering war with City Hall over the blight and late or unpaid taxes. Adding to that is Mendelson's unpaid water and sewer bill, the largest in Allentown. While fighting the city, Mendelson's companies also have been in court over claims that they stiffed other businesses for sums ranging from a few hundred dollars to more than $1 million.

In the meantime, Mendelson has lived a lavish lifestyle in the posh Philadelphia suburb of Villanova, enjoyed a sprawling vacation lodge in the Poconos, owned numerous cars and hobnobbed with powerful Pennsylvania politicians and bureaucrats, even making some of them business partners.

To Allentown's political leadership, Mendelson's record shows only contempt for the city. After 17 years, city leaders said, the feeling is mutual.

''I'd love to see him leave town and I'd love to help him leave,'' said Mayor Roy Afflerbach.

But once Mendelson settles in, he is not easy to move.

''I've survived a lot of mayors,'' he said. ''I'll survive more mayors.''

How can someone who allows his properties to rot and mind-boggling bills to go unpaid survive and thrive, even capturing contracts financed by state taxpayers?

The man in question does not provide easy answers. In three telephone interviews, Mendelson spoke in measured tones, but was combative, threatened lawsuits and suggested that his detractors are bigots who discriminate against him because he is Jewish. He characterized himself as a victim, pinning the responsibility for the decline of his businesses and the local economy on city leaders. He also declined to discuss most details of his businesses or even past projects.

''I'm a private company. I don't need to disclose what I've done,'' he said.

But an investigation by The Morning Call based on an extensive review of public records throughout Pennsylvania and beyond and interviews with dozens of those who have worked with Mendelson reveals a record of audacious development plans and stunning failures.

Along the way, Mendelson has developed patterns in support of his business dealings. A pattern of supporting politicians and forming partnerships with current and former high-level bureacrats while at the same time withholding taxes to the governments they run. A pattern of delaying payment or failing to pay debts while seeking — and sometimes getting — deals to ease his own liabilities.

Property records also show that in spite of their inactivity and deterioration, Mendelson's Allentown properties have continued to work for him, acting as collateral for tens of millions of dollars in loans — far more than what he paid for them. As recently as October 1999, he secured a loan of $3.5 million using one of them as collateral.

Allowing Mendelson to function despite his properties' decline have been city officials who at first welcomed his attempts to revive downtown but found themselves overwhelmed and outgunned once things went bad.

But even for a developer with such a controversial record, the year 2002 is shaping up to be a particularly bad one in Allentown. Consider:

Code violations sent guests at the Americus packing in August. Inspectors said the 13-story building needs new plumbing and fire sprinkler systems. Meanwhile, Lehigh County is suing over unpaid occupancy taxes from the months when the hotel had guests.