Concierge.com's insider take:
Locals like to call it the "Eighth Wonder of the World," and the Panama Canal, completed in 1914 at the cost of $375 million and 5,609 human lives, really is an engineering marvel. Just south of Panama City in the town of Balboa, you can drive across the graceful Bridge of the Americas spanning the canal's mouth, and look down on the massive container ships moving in and out of the bay. But for a closer look at the locks that raise and lower to let the ships through, go to the Miraflores Visitor Center, about 20 minutes' drive north of Panama City, at the eastern edge of the Miraflores Locks (507-276-8325; www.pancanal.com/eng/anuncios/cvm/index.html).
If you want to navigate the canal itself, you can take a boat tour with Canal and Bay Tours. But be warned: Much of the canal is nothing more than an oversized ditch. A better option is to take one of the company's bay cruises, which take in some beautiful scenery as well as the entrance to the canal (507-209-2009; www.canalandbaytours.com).
The Barro Colorado Nature Monument, a world-renowned biological preserve, sits on Isla Barro Colorado, in Lake Gatun—the reservoir that feeds into the canal. Here you'll find about 100 species of mammal, including five types of monkey native to the country. Tourist access to the island is limited, so you'll need to arrange a visit in advance by contacting Panama's Smithsonian Tropical Research Institute (507-212-8900; www.stri.org/english/visit_us/barro_colorado).