Old St. Mary's Catholic Church

They have a wonderful Mass every weekday at 12:15 sharp. It's a short "workers Mass" and is complete by 12:55 at the latest, so there's no reason for any Catholics working downtown Detroit to miss the Mass. The Church itself is steeped in the history of the city, and is well worth visiting to look around even if you are not Catholic. If you want to just look at the amazing architecture (or say a rosary before Mass) doors are open during the weekdays at 11:00, and stay open until 2:30 after the Mass. Note for sightseeing: There is a Eucharistic adoration after the 12:15 Mass on Fridays and many stay for the hour or so long adoration, this makes it difficult for someone who just wants to sightsee to photograph and explore without disrupting those in prayer.