Trump Tower/ Photographer: Allison Joyce/Bloomberg

NEW YORK CITY—Trump Tower, once the crown jewel in Donald Trump's property empire, now ranks as one of the least desirable luxury properties in Manhattan.

The 36-year-old building has been turned into a fortress since Trump won the presidency, ringed with concrete barriers and the two main entrances partially blocked off. It hasn't been substantially updated in years. And Trump's name has been a huge turnoff in liberal New York City.

For anyone who owns a unit in the tower, the past two years have been brutal. Most condo sales have led to a loss after adjusting for inflation, property records show. Several sold at more than a 20% loss. By contrast, across Manhattan, just 0.23% of homes over the past two years sold at a loss, according to real-estate data provider PropertyShark, although the firm doesn't adjust for inflation.