Many cities around the world offer underground or skyway systems that insulate visitors from the harsh elements: heat, cold, pollution, honking cars. Here are five enclosed mini-metropolises to explore.

· Montreal.The Quebec city's RESO network comprises about 20 miles of underground passageways that link metro stations, theaters, museums, universities, hotels, thousands of boutiques and restaurants, and such major attractions as the Bell Centre. Art adds a decorator's touch to the tunnels.

Info:Tourisme Montreal, 877-266-5687,

· Minneapolis.The city's windowed skyways let in natural light but banish the cold. The walkways are above street level, so you have a nice view of those bundled below. The seven-mile network covers 72 blocks and links to downtown hotels, restaurants, shops, theaters, performing arts venues and more. One drawback: Some of the bridges close after business hours or on weekends.

Info:Meet Minneapolis, 612-767-8000,

· Houston.In Houston's Tunnel, travel high or low, but never in the suffocating Texas heat. The seven-mile system contains concourses 20 feet below downtown as well as skywalks with access to hotels, banks, restaurants and various performing arts venues in the Theater District. Shops and services line the walkways, including boutiques, snack bars and optometrists. The Tunnel is open only during weekday business hours, though a portion can be accessed on weekends. Discover Houston Tours (713-222-9255, offers a Tunnel walk for $20 per person.

Info:Greater Houston Convention and Visitors Bureau, 713-437-5200,

· Osaka.In this Japanese city known for shopping, you can spend countless yen -- and hours -- in sprawling underground shopping arcades centered on subway stations. In addition to thousands of stores, bars and restaurants, there are also art displays, themed streets (Casual Street, Fashionable Street, etc.) and waterfalls. Check out the stores at Whity Umeda, Hankyu Sanbangai, Dojima Underground Shopping Center and Crysta Nagahori.

Info:Osaka Convention and Tourism Bureau,

· Singapore.The Southeast Asian country is known for having high humidity and heavy rains, but pedestrians can keep dry and frizz-free in underground passageways that link many buildings around downtown. The biggest subterranean area is CityLink Mall, which has 60,000 square feet of retail and restaurants and connects the City Hall MRT Station to the Suntec Convention Center, five hotels, a movie theater and another mall.

Info:Singapore Tourism Board, 212-302-4861, -- Andrea Sachs