Drive under the Gatun Locks of the Panamá Canal, head past the active military checkpoint (bring ID!) for the old US Fort Sherman, with its decaying buildings, and on to eerie Fort San Lorenzo, jointly UNESCO-listed with the forts of Portobelo. Much of the riches of the Americas pass through Panamá during Spain’s heyday and these forts saw treasure and pirates.
Fort San Lorenzo is deserted and peaceful, until the haunting animal calls begin.
Combined with the Gatun Locks it makes an excellent day trip from Panamá City, though nearby city Colón has little to recommend and there are reports of safety issue. Of course I got greedy and pushed on to Portobelo!