On March 10, Osaka was enjoying its status as Japan’s third-largest city and one of its biggest ports. As the headquarters for almost 100 companies — including Asahi Broadcasting, Hitachi Zosen, Panasonic, Daihatsu, Mitsubishi, Sanyo Shimano and Tsubakimoto Chain — Osaka was also known for its business-friendly environment, second only to Tokyo as Japan’s commercial center. And among Japanese citizens and some foreigners, it also had a reputation for great cuisine. Since the Edo period, the city has been called “Japan’s kitchen” (tenka no daidokoro) because of the presence of the country’s first rice market; the high number of Michelin-starred restaurants in the city today — 90 — has only confirmed its standing as a place where high-quality food defines the dining scene.

One day later, however, on March 11, the earth around Japan moved, and the northeastern city of Sendai and surrounding areas were hit by an earthquake and massive tsunami, followed by the destruction of the Fukushima Daiichi Nuclear Power Station. Osaka became Japan’s “go-to” city. With Tokyo incurring structural damage, airport and rail shutdowns and fears of encroaching radiation from the affected areas, a migration took place. Corporate executives, governmental agencies, international businesses, travelers and air carriers quickly began moving operations from Tokyo, 165 miles from Sendai, to Osaka, almost 400 miles from the affected areas.

There were rolling blackouts throughout Tokyo; long-distance trains halted outside the city, Disneyland Tokyo closed for one month, and flights were diverted from Tokyo’s Narita International Airport to Osaka’s Kansai International. Osaka, which saw no damage to its infrastructure, became Japan’s “host” city as hotels took in a surge of Tokyo refugees, grandparents found their out-of-town children and grandchildren at their doorsteps, and pregnant women afraid of radiation in northern Japan left their husbands at home to settle in with relatives or friends in Osaka.

As more Japanese and international visitors found themselves taking shelter in Osaka, often for weeks and months at a time, the city’s reputation began to change. No longer considered a business-only city, Osaka’s generosity of spirit, its redeveloped waterways, stunning architecture — and in no small part its ability to efficiently move passengers and cargo in and out of the city by air, rail, road and ship — received rave reviews from its new, albeit temporary, residents.

Truck transports, then cargo flights, began to leave Osaka with food, clothing and medical supplies for the Sendai region, and the once “must-have” economic data, corporate news and Osaka Securities Exchange prices emanating from the local news media suddenly became much less important as the city mourned the country’s unimaginable losses and went about its business supporting the rescue process.

Osaka was designated Japan’s first capital in the seventh century, and although the capital was later moved to Nara, Kyoto and finally Tokyo, Osaka had established itself as a center for Japanese business and politics, reflected in the construction of its most famous attraction, Osaka Castle, built in 1583 by Toyotomi Hideyoshi, a unifying political figure in medieval Japan.

Although the popular 16th-century castle is the city’s most iconic structure, and traditional 19th-century Osaka can still be found within the city’s historic Jinaimachi neighborhood and in the quiet gardens surrounding its temples, modern Osaka, with 2.5 million residents, has spread out along rivers, canals and Osaka Bay. A bustling metropolis, it blends into the neighboring large cities of Kobe and Kyoto and hundreds of industrial satellite towns for a total population of over 19 million. The combined Osaka/Kobe/Kyoto metroplex has a gross domestic product of $341 billion, making it one of the world’s most productive regions.

Rising from the ashes after being heavily bombed during World War II, Osaka grew quickly but haphazardly, with bland concrete buildings and elevated highways stretching from its central core along the Yodo River to the outlying suburbs north and east, and south along Osaka Bay. Today, Osaka’s size and variety offer visual juxtapositions that are stimulating and ever-changing, from the lush and quiet Hombo Gardens at Shitennoji Temple to the frenetic, neon-lit nightscape of the Dotombori district where visitors may feel they have landed on the set of the 1982 American sci-fi film Blade Runner.

During the past decade, government-sponsored programs and private investments have led to numerous office, retail and residential building projects, many of them stunning in their architectural creativity and use of green technology. The noted Japanese architect Tadao Ando was born in Osaka, and his office buildings, museums and the spectacular Church of Light are significant landmarks in the city. Osaka’s downtown core is surrounded by natural rivers and manmade canals, and since the popular 2009 event, “Aqua Metropolis Osaka,” the waterfront areas of the city have received lots of attention and upgrading. New wharves have opened up areas for restaurants, entertainment venues and popular river cruises. The Tombori Riverwalk project is almost complete; its shops, open-air cafés and summer concerts are popular attractions for locals and visitors.

Osaka Station City, the city’s biggest downtown development project, is being constructed in stages by 12 Japanese companies and will include high-end office towers, residential apartments, retail space and a deluxe InterContinental hotel and residences.

The first phase, the renovation of Osaka Station, the city’s largest and busiest rail terminal, opened this spring; phase two, expected to be finished in 2013, will include a network of pedestrian streets winding through an urban landscape of greenery and water features. A total of $2.5 billion has been budgeted for the project.

The Japanese government is also expected to approve a plan by Central Japan Railway Co. to construct a super-high-speed, magnetically levitated train that will run between Osaka and Tokyo by 2045. With a top speed of 300 mph, it will take just 67 minutes to reach Tokyo, cutting 51 minutes off the fastest shinkansen (bullet train) on the route today.

Diversions

Because of the city’s 33 different waterways, Osaka is called the ”Water Metropolis.” Aqua-Liner (2-banchi-saki, Chuo-ku, tel 81 6 6942 551) tour boats leave every hour from downtown piers, offering water views of Osaka Castle, Nakanoshima, Osaka Business Park and other riverside attractions.

Osaka Castle (1-1 Osakajo, Chuo-ku, tel 81 6 6941 3044) should be visited on foot, as the grand gates; the turrets; the ornamental roof tiles; and the steep, 90-foot white stone walls are impressive sights.

There are lots of neighborhoods for shopping, from the 1.5-mile line of small shops along Tenjimbashi-Suji to the fresh produce market Kuromon Ichiba (1-15-6 Nippombashi, Chuo-ku), also known as ”Black Gate Market,” where Osaka’s locals and best chefs have been coming for high-quality meat, vegetables, eggs and fruit for 170 years. The trendy boutiques and cafés in Minami Semba attract the 20-something crowd. Be sure to visit the Hankyu Department Store (8-7 Kakuda-cho, Kita-ku), opened in 1929 and now the flagship of Japan’s largest department store chain. The food shops on the lower levels are outstanding.

The National Museum of Art (4-2-55 Nakanoshima, Kita-ku) is great for viewing traditional and new trends in Japanese art, and the Umeda Sky Building (1-1-88 Oyodo-naka, Kita-ku) has a 510-foot-high observation platform on a bridge connecting the building’s two towers. An even higher observatory is the jazz bar on the 55th floor of Cosmo Tower (1-14-16 Nankokita, Suminoe-ku), where a see-through elevator zips to the top for a spectacular 360-degree view of Osaka. Perhaps most symbolic of Osaka’s attempt to redefine the urban lifestyle is Namba Parks, designed by Jon Jerde Partnership as a 30-story commercial tower with a rooftop park and a natural, ground-level park, complete with waterfalls, streams, outdoor terraces, cliffs and rocks. The juxtaposition of natural and manmade — green spaces above and below steel towers, cement versus water, blazing neon against the dark sky — is what makes Osaka so visually appealing.

Info To Go

Kansai International Airport (KI X), about 30 miles from downtown, opened in 1994 on an artificial island in Osaka Bay. Access to city center is by train (35–60 minutes; $11–15), bus (50–95 minutes; $14–18) and taxi (50–60 minutes; $195–208). Do not confuse Kansai with Osaka International Airport (ITM ), Osaka’s original city airport that now handles only domestic flights. For more information, visit www.osaka-info.jp or www.jnto.go.jp.

Lodging

RIHGA Royal Hotel Osaka

The Japanese company’s flagship property has executive floors, a large sauna and pool, a fitness center, conference rooms and the highly rated Restaurant Chambord. 5-3-68 Nakanoshima, Kita-ku, tel 81 6 6448 1121 $$$$

The Ritz-Carlton, Osaka

This posh property within walking distance of Osaka Station has two Michelin-starred restaurants, a heated indoor pool, steam and dry saunas and a business center. 2-5-25 Umeda, Kita-ku, tel 81 6 6343 7000 $$$$

Swissôtel Nankai Osaka

The deluxe 548-room hotel offers an Amrita Spa with an indoor pool and Japanese-style baths, executive club floors, a rooftop Sky Bar and nine restaurants. 5-1-60 Namba, Chuo-ku, tel 81 6 6646 1111 $$$

Dining

Hanagatami

Hanagatami serves kaiseki cuisine as well as sushi, tempura and teppanyaki. Private tatami rooms, a saké sommelier and exceptional service enhance the experience. The Ritz-Carlton, 2-5-25 Umeda, Kita-ku, tel 81 6 6343 7000 $$$$

Miyoshiya

One of the best handmade udon (wheat noodle) shops in the city uses all-natural ingredients and offers udon cooking lessons. 9 9-17 Namba Sennichimae, Chuo-ku, tel 81 6 6643 2220 $$

Taian

Promoted to three Michelin stars last year, Taian has only 12 counter seats and one table for four; reservations are necessary via phone or hotel concierge. 1-21-2 Shimanouchi, Chuo-ku, tel 81 6 6120 0790 $$$$