Washington (CNN) Trump Tower in Manhattan, home to President-elect Donald Trump and a fixture of American politics for the last 18 months, has become a de facto "fortress" as security measures go into place for the incoming president.

As Trump's top aides and leaders of the transition team headed to the new executive's New York headquarters Friday, they were met by jersey barriers and concrete blocks set up by police. And a large police presence was established on the block surrounding Trump Tower, limiting public access.

Securing Trump Tower, in the heart of Manhattan, has become a challenge for New York police and the Secret Service.

The entrance to Trump tower -- which sits near heavily trafficked luxury shops, including Tiffany & Co. and Gucci -- has become a special challenge. New York City zoning rules require that the space in front of Trump Tower remain open to the public, and Secret Service officials say they have told city officials they are trying to be mindful of any impact on business.

Secret Service officials have raised the possibility of shutting down some lanes on Fifth Avenue -- or even shutting down the major thoroughfare entirely -- in talks with city law enforcement.