It's all part of New York City's Summer Streets program.
On Saturday, people were able to walk through the 1,300 foot-long tunnel to experience a voice-activated light show.
The tunnel was open to pedestrians between 33rd and 40th Streets.
Parts of Park Avenue and Lafayette Street will be closed to traffic for the next three Saturdays for various family-friendly activities.
Vehicles will be temporarily banned from the tunnel so it can be turned into an interactive light and sound installation.
The New York Times (http://nyti.ms/15qX3uR ) says visitors will be instructed to walk midway and speak into a silver intercom. Their short messages will travel outward in waves of sound and arching light until they disappear.
The messages will come in quick succession, creating a rapidly changing ebb of sound and light.
The pitch of each visitor's voice will determine the intensity of each beam.
The creator is Rafael Lozano-Hemmer. He's known for his large-scale interactive art.