Indonesia is a vast nation, consisting of 17,000 islands that stretch for more than 3,000 miles. It has 235 million citizens -- the fourth-largest population in the world -- and those citizens speak more than 500 languages.

Can you imagine the investment opportunities that come with serving such a large and varied market? If you answer "no," you're not alone. Indonesia flies under the radar of most Western investors -- and most businesses, for that matter.

Here's why we should be paying attention.

A growing opportunity
Like many of its Southeast Asian neighbors, Indonesia is growing rapidly. Growth in real gross domestic product -- which subtracts the effects of inflation -- is averaging an impressive 6% annually, compared with 2.2% in the United States. The Economist Intelligence Unit predicts that real GDP growth will average 5.9% over the next five years, driven by growing foreign investment and consumer spending.

In other words, Indonesia is just getting started.

As a result of the strong economy, stock-market returns have been blistering, with the Jakarta Stock Exchange up nearly 400% over the past five years, led by industry titans such as Telkom Indonesia (NYSE:TLK), Indosat (NYSE:IIT), and Bumi Resources.

Two of the hot sectors in Indonesia are telecommunications and energy. Telecom is obvious; cellular technology is crucial for connecting a country made up of thousands of islands.

Indonesia is also blessed with substantial natural resources, including oil, thermal coal, iron ore, and nickel. Its status as an OPEC member demonstrates just how much oil exists in Indonesia. Its recent decision to leave the OPEC club is even more telling -- because of years of underinvestment in its energy infrastructure, Indonesia has become a marginal player in the export of its oil.

The smart money is rushing in overseas
Given all of these opportunities, companies across the globe -- including India's Reliance Power, China's Guohua Electric Power (a subsidiary of China Shenhua Energy), and India's Tata Power -- are tripping over each other to invest. Lakshmi Mittal, head of Arcelor Mittal (NYSE:MT), is reportedly planning to invest as much as $10 billion in nickel, iron ore, and other projects.

Western companies, however, have had mixed success in Indonesia. For example, Intel (NASDAQ:INTC) endured a lengthy court battle, and ExxonMobil (NYSE:XOM) lost the right to develop a gas field under unclear circumstances.

Foolish final words
It all goes to show that although the potential rewards in Indonesia are sky-high, the risk in commensurate with its status as an emerging market.

It's a market you shouldn't overlook any longer, but it's also not all that accessible to U.S. investors right now. According to Capital IQ (a division of Standard & Poor's), there are only two Indonesian companies available on our major U.S. exchanges -- the aforementioned Telkom Indonesia and Indosat. The closed-end Indonesia Fund (IF) is the only other "pure" option.

Your best bet otherwise is to look for multinationals with operations in Indonesia. ArcelorMittal is one such example, as are ConocoPhillips (NYSE:COP) and Procter & Gamble (NYSE:PG), which both have Indonesian subsidiaries.

Our Motley Fool Global Gains team is headed to Indonesia and other parts of Asia this week to view firsthand the compelling growth and to unearth potential opportunities in one of the largest, most diverse markets in the world.

Want to know what we find? Sign up for our team's free dispatches from the road. All you have to do is enter your email address in the box below.