Grand Central is not only the world's largest railway station (76 acres) and the nation's busiest (500,000 commuters and subway riders use it daily), it's also one of the world's greatest public spaces, "justly famous," as critic Tony Hiss has said, "as a crossroads, a noble building… and an ingenious piece of engineering." A massive four-year renovation completed in October 1998 restored the 1913 landmark to its original splendor -- and then some.

The south side of East 42nd Street is the best vantage point from which to admire Grand Central's dramatic beaux-arts facade, which is dominated by three 75-foot-high arched windows separated by pairs of fluted columns. At the top are a graceful clock and a crowning sculpture, Transportation, which depicts Mercury flanked by Hercules and Minerva. The facade is particularly beautiful at night, when bathed in golden light. Doors on Vanderbilt Avenue and on East 42nd Street lead past gleaming gold- and nickel-plated chandeliers to the cavernous main concourse. This majestic space is 200 feet long, 120 feet wide, and 120 feet -- roughly 12 stories -- high. Overhead, a celestial map of the zodiac constellations covers the robin's egg-blue ceiling (the major stars actually twinkle with fiber-optic lights). A marble staircase modeled after the Garnier stair at the Paris Opera is on the concourse's east end. Climb it to reach Metrazur restaurant. From this perch you can look across the concourse to the top of the opposite staircase, where diners treat themselves to either Cipriani or the mahogany-and-leather setting of Michael Jordan's Steak House. Beyond those two restaurants to the left you'll find the Campbell Apartment, an extremely comfortable and stylish cocktail and cigar bar in what was once a rather secretive pied-à-terre.

The Grand Central Market on the east end of the main floor (a street entrance is on Lexington Avenue and East 43rd Street) is a great place to buy fresh fruit, fish, dairy goods, and breads. Dangling from its amazing inverted olive tree are 5,000 glass crystals. Dozens of restaurants (including an outpost of the popular Brooklyn deli, Junior's, and the mammoth Oyster Bar) and shops, many in spaces long closed to the public, make the downstairs dining concourse a destination in its own right.

Despite all its grandeur, Grand Central still functions primarily as a railroad station. Underground, more than 60 ingeniously integrated railroad tracks lead trains upstate and to Connecticut via Metro-North Commuter Rail. The subway connects here as well. The best (and worst) time to visit is at rush hour, when the concourse whirs with the frenzy of commuters dashing every which way. The most popular point for people to meet is at the central information kiosk, topped by a four-faced clock. The Municipal Arts Society (457 Madison Ave., PHONE: 212/935-3960; www.mas.org) leads architectural tours of the terminal that begin here on Wednesday at 12:30. A $10 donation is suggested. Subway: 4, 5, 6, 7, S to 42nd St./Grand Central.