Costa Rica & Panama
If you dream about eco adventure, hot springs in the shadow of a volcano, sloths, ziplines and coffee, not to mention your choice of Pacific and Caribbean beaches, then Costa Rica should be high on your list. A quick flight to the south, Panama with its military history, feats of Canal engineering and continued use of the US dollar, makes it an Ex-Pat paradise with frequent and easy flights from the states & no money exchange.
It's possible to base camp in Capital City San Jose and see the Volcanoes, Cloud Forests and Coffee Farms of Costa Rica on a string of day trips. But staying in some of the world's premiere Eco Resorts and waking up to the sound of howler monkeys and poison dart frogs is next level. There is also a terrific surf scene, and lazy beach days to recover from all the adventures.
Of course the star here is the Panama Canal, including both the old locks (engineered over 100 years ago by the US Army) and the new lock system, created to accommodate today's massive ships. To learn more, the Panama Canal museum in the old town is a great learning stop, along with the Spanish Colonial sites on both coasts. If the glitz of a vibrant modern shopping and casino skyline is more your scene the "new" city will give glam with a Miami feel.
Sail Between them for a unique experiance
Plenty of cruise-ships of all sizes offer this itinerary as a combo, which shows you a whole different side of Costa Rica - like the otherwise hard to reach mangrove forests, animal sanctuaries and Pacific Ocean water sports. Once in Panama, you'll see the up close and personal working side of the Canal as your ship actually queues for passage, and then enters the lock system to be moved across the Peninsula.