The capital of French Guiana is CAYENNE, which is a seven-letter word. CAYENNE is the largest city in French Guiana and is located on the Atlantic coast. It is the cultural and economic center of the country, and is home to many of the government offices. The city has a rich history, having been colonized by the French in 1643. It is known for its diverse population, with people from many different backgrounds living in the city. CAYENNE is also a popular tourist destination, with many attractions such as the botanical gardens, the old fort, and the local markets.