Mountains To Sea Trail

One of the few pleasures of Orange County not involving shopping or eating. And a true pleasure it is. Most parts (especally in Tustin and Irvine) are good for rollerblading as they are newly paved. But the pavement gets bumpy in the Back Bay – not to mention the vicious downhill into Back Bay, which most beginner and intermediate skaters make on foot or zigzagging with care.

Runs from Orange, through Tustin and Irvine, parallel to San Diego creek, past the wild bird sanctuary, UCI, into the Back Bay, past Newport Dunes and all the way to the beach at Balboa (uphill on Jamboree, over PCH, through Balboa Island and crossing the Newport Bay by ferry).

More details here, here and on various MTB sites.