Hidden behind a giant office building facade is this enormous and elegantly designed Hunan restaurant, and behind it is an excellent kitchen. The space is not as imposing as it sounds, for it is carved into several rooms and smaller divided areas, and the tables are definitely too close together. The menu is by now familiar to China hands -- beef with orange, fried shrimp balls, hot and sour soup, pork with garlic sauce or double-cooked, and so on. What is uncommon is the cooking: The hot-and-sour soup is complex underneath its heat and tartness, and suffers from none of the gluey quality too often encountered. The shrimp balls are light and greaseless, and orange beef is as tender as one could want, with a lovely thin and crunchy crust. The lobster has tasted a little tired, and the heat level in the asterisked dishes overall is low for a Hunan kitchen. The imposing and grand service can edge into being pushy and overbearing -- I would ask to portion the dishes myself rather than have the waiter pile them all up on our plates. But Hunan is a restaurant of skill and ambition and, nlike some of the glamorous new Chinese dining rooms, warrants its high prices. 2070 Chain Bridge Rd., Vienna, Va. 734-9828. L $5.25-$7.50, D $7.25-$23-95. L daily ex Sun, D daily. AE, CB, DC, MC, V. Res sugg. Full bar.