Greek Orthodox church with amazing frescoes
The Santos Andrés y Demetrio Greek Orthodox Church is a criminally-unknown artistic gem located in the neighborhood of Colombia, an area which most tourists only pass on their way to and from the airport. The church itself is open at odd hours, usually from around 6:00pm to 8:00pm during the week and at 9:30am on Sundays, but don't hold me to that because precise opening information for the church is difficult to find.
The church is a Unitarian Greek Orthodox church meaning that all are welcome in its halls, no matter their denomination or precise ideology. That being said, it's a decidedly Eastern church: the majority of the worshipers from the Balkans, Greece, and Russia, a big bearded priest dressed in black chants hypnotic liturgy throughout the service, there are candles lit in front of icons of obscure saints, and the older, more traditional female worshipers attend with their heads covered. Still, I attended a service and was welcomed warmly by the old woman at the door and offered a candle to place at the altar.