You needn't be of strong faith to appreciate the calming atmosphere of Sacred Heart Cathedral. Look up when the next service is scheduled or when it's open for general viewing.
Sacred Heart Cathedral is an interesting place to begin exploring Porto Velho. This principal church is recommended by fellow travelers, but it isn't the only spot to see here. Pencil in time for other sights like Ivan Marrocos Cultural Center, Estrada de Ferro Madeira-Mamoré, and Parque Natural de Porto Velho to fully appreciate what the area has to offer.