It is probably the most surprising restaurant in the city, for Spectrum hides behind an ordinary facade a mere half-block from the convention center. And inside is one of the prettiest and most sophisticated of Washington's moderately priced restaurants, and very good food including some of the best Mexican dishes hereabouts.

The dining room is long and narrow, with glass tables covered in white cloths. Marching along the ceiling are neon tubes banded with various colors.

The menu at Spectrum is about half Mexican/Latin (ceviche, guacamole, black bean soup, enchiladas, chicken with mole) and half continental, from veal marsala to mussels steamed with wine to fish meuniere. The surprise is that it is all good. I've had a smooth and well-balanced black bean soup as good as that can get, and a fine chunky and zesty guacamole in a pretty, crisp tortilla cup. And haddock sauteed with lemon and capers was no less delicious. In case you want to be picky, the filling for the empanadas is rather pasty and bland. Except for the spongy rolls, the details are shown as much care as the main fare; vegetables are fresh and bright and perfectly cooked. Even the coffee is particularly good, brewed from espresso beans. And the service is personable and attentive, though the kitchen can run slow.

Spectrum is a satisfying cross between a neighborhood ethnic restaurant and upscale downtown dining. And it is certainly worth a trip from much farther away than the convention center. 919 11th St. NW. 638-7505. L $5.50-$9.75, D $8.50-$10.95. L daily ex Sat, D daily. Closed Sun. AE, DC, MC, V. Res sugg. Full bar.