If you are in Panama you can’t miss a walk in the Old Quarters (Casco Antiguo) and learn about the amazing history of the Isthmus. The beautiful architectonic styles, narrow streets and cafes will fascinate any traveler looking for a bit of authenticity in this cosmopolitan Panama City. In colorful Casco, the Spanish and French colonial houses mixes with the art deco and neoclassical style. If you go for the first time, don´t miss the Church of the Golden Altar and the Flat Arch.
The Golden Altar: The massive golden altar (altar de oro) is a prime tourist attraction at Iglesia de San José (Avenida A between Calle 8 and Calle 9, 7 a.m.– noon and 2–8 p.m. Mon.–Sat., 5 a.m.–noon and 5–8 p.m. Sun.). Legend has it that the altar was saved from the Welsh pirate Henry Morgan during the sacking of the original Panama City when a priest ordered it painted black, hiding its true value.
The Flat Arch: The original Iglesia de Santo Domingo (Avenida A and Calle 3 Oeste) was built in the 17th century, but it burned twice and was not rebuilt after the fire of 1756. It remains famous for one thing that survived, seemingly miraculously: the nearly flat arch (Arco Chato). Since it was built without a keystone and had almost no curve to it, it should have been a very precarious structure, yet it remained intact even as everything around it fell into ruins. One of the reasons a transoceanic canal was built in Panama was that engineers concluded from the intact arch that Panama was not subject to the kinds of devastating earthquakes that afflict its Central American neighbors.
Source: Moon guides.