Santissimo Sacramento e Lorenzo Martire is a deconsecrated Baroque chapel or oratory at Via Belsiana 48/B, just east of the Corso in the rione Campo Marzio. Picture of the church at Wikimedia Commons here.
The oratory used to belong to a Eucharistic confraternity, attached to the parish of San Lorenzo in Lucina and founded in 1576. They erected it two years later, together with adjacent premises for their secular activities. It was remodelled, perhaps by Nicola Michetti, in 1724.
Towards the end of the 19th century it became a noted venue for concerts of Baroque music while remaining a functioning oratory. However, it was finally deconsecrated in 1970 and is now a shop called Gherardini.
The plan is of a simple rectangle. Unusually for an oratory, there is a crypt and hence the entrance is approached by a flight of stairs. Round windows on either side of this light the crypt.
The simple façade has two pairs of rectangular pilasters without capitals, supporting an entablature which has a dedicatory inscription on the frieze and a projecting cornice. There is a roundel in relief between each pair, midway up.
The doorway is surrounded by a thin ribbon string course, and this continues up with a couple of flourishes to run under a low floating archivolt in relief. There is no other decoration.
Apparently, when it was a functioning oratory it contained nothing worth a visit to see - non contiene opera d'arte.