Downtown’s Fourth Avenue changes its skin at the drop of a hat depending on the hour. Nothing sexy there, as the Gaslamp Quarter’s western boundary is caught up in the area’s bustle as surely as Fifth and Sixth, which are clearly in the thick of things. There’s a schizoid flavor about it all on the latter two thoroughfares — the light of day persists in tracking the whereabouts of button-down shoppers and businessmen, many of whom then duck into hip, iconic watering holes and lose total control under cover of darkness. Fourth Avenue itself, however, is more settled than all that. The majestic Balboa Theatre, reopened in 2008 as the last of the Horton Plaza projects after a retrofit and a 20-year hiatus, sets a lot of the tone for today’s Fourth. It’s vibrant in the classical sense, its newest and prospective establishments leaving the cool factor to the others. “Fourth Avenue is kind of an informal theater district,” explained Brad Richter, Centre City Development Corporation’s assistant vice president of current planning. “Fifth Avenue is concentrated more toward the nightclubs, and then on Fourth and immediately west, you have the more mature crowd, for lack of a better term. It’s more of a destination, with the theaters like the Balboa and the Lyceum and the (nearby) Civic there.” Indeed, amid prospects for a new federal building and state court center in the area to the west, the ubiquitous condos springing up to the west and north, and even a new streetlights plan that touches on the thoroughfare, Fourth remains relatively untouched. The only major construction agenda around Fourth, Richter said, is the northerly Lower Cortez Hill area. That’s the site of a new neighborhood park, just south of St. Joseph’s Cathedral. “There will be a lot of mixed-use developments around there,” Richter said, “primarily residential.” In all its basic intactness, Fourth Avenue’s major monument to urban blight remains the California Theater, in the avenue’s 1100 block. Slated for demolition in 1990, the place is a doddering, caliginous mess, now the property of a financial company that’s working with the city to evaluate the building’s structural integrity. “A lot of people have looked at that block, including the owners of the 4th & B concert venue,” Richter said. “Hopefully, somebody will be able to put together a development plan that involves the whole block.” Meanwhile, Fourth Avenue remains set in its ways, a stubborn alternative to the Gaslamp’s traditional flash and dash. “The Gaslamp Quarter is known as a bustling dining destination, and we are glad to be a part of it, and bring something different to the table,” Bice general partner Trevor Sacco said. The “different” part is in the ambience — a quiet, genteel, unadorned setting rich in the sedateness that any viable theater district, and indeed Fourth itself, exudes.