These are the ruins of Panama Viejo, the original Panama City from 1519 to 1671. After Captain Morgan and company destroyed the city, the Spanish rebuilt the city at Casco Viejo (see previous posts). Beginning in 2000, the Panamanian government along with the Spanish government and UNESCO embarked on a project of restoration (hence the rebar, cement, and cleaned bricks in pictures).
Who says nothing beautiful ever comes from war? We really enjoyed the ruins. Maybe more cities should be burnt to the ground...