Panama City's oldest surviving neighborhood is also its most defensible, a tejas-tiled cluster of primly painted colonial buildings at the tip of a heavily fortified peninsula. These ramparts successfully protected the first Spanish settlement on the Pacific Coast, today a UNESCO World Heritage Site.
After decades of neglect, Casco Viejo is finally being revitalized. New hotels and restaurants, some quite elegant, are occupying the centuries-old buildings. Iconic landmarks like El Arco Chato (Flat Arch), which may date to neighborhood's founding in 1671; the 1798 Metropolitan Cathedral; and many other pretty plazas, palaces, markets, and gold-gilt churches have been refurbished, as have the narrow streets, draped in flowery French balconies, which connect them. Well worth a wander.
While the Casco Viejo is well into the process of gentrification, surrounding neighborhoods are not - they are gritty.
Take a taxi, even during the day, unless you're quite comfortable with impoverished areas such as those that surround the old town.