WILLIAMSBURG - The Brooklyn Navy Yard gives many tours throughout the year, but tours at the 300-acre site are offering a unique twist starting this weekend.

The site is hosting urban ecology bicycle tours. Participants begin at the Navy Yard's Building 92 and pedal past an urban rooftop farm, the waterfront and an oyster farm.

Today was the first of these tours, but the Navy Yard will offer them every weekend. They cost $30, and bikes and helmets aren't included.