Most of the historic sculptures, frescoes and edifices of early-15th-century Florence are not the least bit portable. It's simple: You want to see them, you go to Florence. But right now nearly a third of one of the city's greatest glories can be seen without leaving town, by visiting “The Gates of Paradise: Lorenzo Ghiberti's Renaissance Masterpiece” at the Metropolitan Museum of Art.This show presents 3 of the 10 gilded bronze reliefs that decorate the doors created by Ghiberti from 1425 to 1452 for the 12th- to 13th-century Baptistery of San Giovanni. Newly cleaned, they have never looked more golden or less oldie.One of the treasures of the early Renaissance, the 17-foot-high doors depict Old Testament scenes in a radically new fusion of physical action, emotional intensity and narrative complexity. Especially the three reliefs at the Met. Their subjects are Adam and Eve, Jacob and Esau, and David and Goliath. Each is pictorially unified and yet, in a different way, almost cinematic in effect.Early-15th-century Florence was the center of artistic competition, thanks to a singular confluence of talent, ambition and money. Artists were engaged in an aesthetic space race, as sculptors pursued free-standing, in-the-round figures, and painters one-point perspective. Sculptural relief hovered deliciously somewhere in between.Artists grasped that convincingly dimensional renderings of figures in space expanded art's communicative powers. Their competition was abetted by the wealthy guilds, eager to outdo one another in expressions of civic pride and religious devotion. In this race Ghiberti's achievement was something like putting a man on the moon.In 1425, when the wool merchants' guild of Florence commissioned its second set of gilded bronze, relief-covered doors for the Baptistery, it spared no expense but took few risks. The job went to a known quantity, Ghiberti, who had already distinguished himself with an earlier set of doors, created from 1403 to 1424.It will never be known how much money the guild lavished on the project, which consumed 27 years of Ghiberti's life and involved scores of artisans. When he died at 77, three years after the doors were completed, he was the richest artist of his time. But Ghiberti also outdid himself artistically, working, he would later say, with “the greatest diligence and the greatest love.” His first and second sets of doors vividly encapsulate the transition from the international Gothic style to a more classically based, early-Renaissance mode. The numbers alone are telling: His first set covered its New Testament themes with 28 reliefs, each mostly using three or four figures seemingly perched on little shelves; the second set depicted most of the Old Testament high points in 10 larger reliefs, whose ground planes slant out and down, implying continuity with the viewer's space.Ghiberti did away with the Gothic quatrefoil frame that had left the outer edges of the first reliefs blank. The second set expanded the action to the edges of the relief, a breakthrough that Ghiberti probably gleaned from Donatello, his former student, when both worked on the cathedral in Siena.The open scheme allowed for more figures, more action and more space. As important, it brought out Ghiberti's sublime talent as a dramaturge, an ability to compress narrative and weave together sequences of events without visual confusion.“Adam and Eve” is set in the Garden of Eden, a reasonably shallow landscape where the magnificent figures of Adam, Eve and God put in multiple appearances. On the left, God, looking like an Old Testament prophet, creates Adam; in the center, God extracts a full-bodied, appropriately drowsy Eve from Adam's rib. (She is nearly a dead ringer for Botticelli's “Venus Rising.”) In low relief in the background, at left, the couple flank the Tree of Knowledge; Eve is alert, eyeing the apple in Adam's hand, egged on by a human-headed serpent. Finally, on the far right, they are driven from the garden. Now God floats above, wearing a bishop's miter. His host of angels is led by an angry seraphim, flying through Eden's arched entrance with his additional wings neatly folded to clear this narrow structure.“Jacob and Esau” depicts Jacob talking his hungry brother Esau into trading his birthright for a mere bowl of pottage and then duping their father, the blind Isaac, into giving Jacob his blessing. The story unfolds in and around a magnificent arched structure that defines pictorial space with a new clarity. “David and Goliath” offers a cast and a battlefield so vast that Cecil B. DeMille must surely be just off-camera. We arrive as David is beheading Goliath; in the background we see David again, head in hand, being joyfully greeted at the gates of Jerusalem.Ghiberti's feeling for physical detail and emotional nuance keeps his surfaces alive, edge to edge. As Adam and Eve's story unfolds, for example, angels register everything from joy to skepticism to alarm. (An angel watching God awaken Adam seems to be asking, “Does he know what he's doing?”) Except for the majestic Isaac, the figures in “Jacob and Esau” dart about, varying in movement, scale and spatial depth, but the palatial structure keeps them separate and clear. The space in “David and Goliath,” an edge-to-edge scrum of fighting soldiers, is created with the overlapping forms of men, horses and weapons, and elaborated by minute details like the changing armor patterns.Some may be disappointed that all 10 of Ghiberti's reliefs did not make this first and only American tour. (The Met is the third of four stops.) But the three reliefs here, accompanied by a life-size photo panel of the fully assembled doors, can by themselves sustain multiple visits. You have until the middle of January.