The Camino Real, the royal road that Spain built across the Isthmus of Panama in the sixteenth century, is the reason this country matters in world history. Gold and silver from Peru were carried by ship to Panama City, loaded on mules and carried over the continental divide to the Caribbean coast, then shipped to Spain. The route had two arms: a paved mule road, the Camino Real, to Portobelo, and a mixed river-and-trail route, the Camino de Cruces, which used the Chagres River for part of the way. Together with the forts that guarded them, the Caribbean forts at Portobelo and San Lorenzo are on the UNESCO list, listed in 1980.
For a rider, the Caribbean end of the story starts around Colon, a rough and rundown city at the mouth of the canal. The road from Panama City, crossing the isthmus in roughly an hour and a half, passes the Gatun Locks, where a steel swing bridge takes you across the canal chamber while ships rise and fall. Beyond it, narrow roads lead through jungle toward the Chagres River and the old fort at San Lorenzo, past howler monkeys, toucans and troops of white-faced capuchins. The tarmac is patchy, with potholes, and heavy rain from May to December can leave it slick.
The isthmus is narrow, and that is the whole point. Standing on a hillside you can nearly imagine how the Spaniards, pirates and later gold-rush travellers all squeezed through this one gap between the oceans. The English privateer Henry Morgan came this way in 1671, capturing the fort at San Lorenzo and marching across to burn Panama City. The old Spanish city is now a ruin, and a newer capital stands further along the bay.
Practical matters need care. Colon has fuel and a handful of restaurants, but it has a reputation for petty crime, so keep valuables out of sight and avoid walking at night. The jungle stretches have few stations, so fill the tank before leaving the main road. The dry season, from January to April, makes for the easiest riding. The humid heat is strong all year, and a rain jacket is always useful.