The Caribbean island of Puerto Rico is truly an intriguing place, as I discovered on my two recent trips there. The rich history of Old San Juan, numerous beautiful beaches, the tropical rainforest El Yunque and the Bioluminescent Bay are just some of the attractions for a relaxing holiday.

The main news out of Puerto Rico these days, however, is the island's $72 billion debt. On Dec 4, the US Supreme Court agreed to consider Puerto Rico's appeal of a ruling forbidding the use of a US law that would allow it to declare bankruptcy and restructure its debt.

Unlike a formal US state, Puerto Rico, which became a United States territory in 1898 following the US invasion in the Spanish-American War, is not allowed to declare bankruptcy.

In his address to the UN General Assembly in September, Cuban leader Raul Castro called for the independence of Puerto Rico. But the independence movement there is now supported by a minority of its 3.6 million people, most of whom speak Spanish rather than English.

Puerto Rico looks not American in the language spoken there, but more in that it is one of only two places in US territory where the metric system is used. The other is Guam, which the US took from Spain in 1898.

At gas stations in Puerto Rico, prices are listed as dollar per liter, rather than per gallon, as in the continental US. In measuring distance and weight, kilometers, meters and kilograms are used instead of miles, feet and pounds.

While these signs may make American tourists feel quite foreign in a US territory, it makes international travelers much more at home.

Having studied, worked and lived in the US for years, I have no sense that 7-foot-6 actually is the height of a 2.29-meter tall guy like Yao Ming, and I have to do my math in filling out a form about my height in feet instead of meters.

The weather app on my iPhone is displayed in Celsius, instead of Fahrenheit, because I am still not quite numerate in telling the high of 55 F on Sunday is 13 C to be exact.

I am not alone among the many Chinese and people from other countries traveling, studying, working and living in the US, as the US remains one of only three nations in the world that have not adopted the metric system. The other two are Myanmar and Liberia, both Third World nations.

The US was in fact one of the original 17 signatory nations in 1875 to the Metric Convention, or the Treaty of the Metre. The US Congress in 1975 passed the Metric Conversion Act to coordinate and plan the increasing use of the metric system in the country, but so far progress has been extremely disappointing.