While the habitable buildings of Antigua look like ancient ruins, there are actual ancient ruins scattered around the city. Correction, there's an abundance of ruins around the city. After the 1773 earthquake, most of Antigua was destroyed. It was so destroyed that Antigua was no longer the capital. The rebuilding process began, but some structures were left in their ruined state. Today there are a bunch of ruins around Antigua that tourists are encouraged to visit. The coolest thing about these ruins (coolest in my opinion), is that you can explore basically anywhere around the sites. There isn't much roped off. Unfortunately, that also means the ruins aren't kept as well as they should. It still doesn't take away from the experience. I highly recommend Convento la Recoleccion (Q40).