Research has allowed us to localize the medieval parts of the Chapel of the Holy Cross, to enrich our knowledge of the history of its construction and to explain the origins of the visible features. The east and west walls of the 15th century chapel have survived in fragments. The detail of the interior finish from the late 16th - early 17th century with text and figural painting on the east wall over the former altarpiece is a valuable discovery. Regardless of the accuracy of dating, the painting occupies an exceptional place in the history of sacral interiors in Riga because no figural interior paintings from the early-mid 17th century had so far been found. The base of the church altarpiece and parts of clay tiles covering the chapel floor has also been discovered. Excavation sites have revealed that the earth inside the chapel has been replaced during repeated digging in the 16th century. So there is little hope of discovering any burial plaques in the future. Vestiges from the Lyceum period are two windows of the east wall and floorboards on the 1st floor. It is clear that the present image of the building is that of a warehouse that has stood here for more than 200 years. Firstly, this impression is created by the division into two floors as well as the window and door frames from 1867, the open roof constructions and parts of a goods hoist. The warehouse interior also features various signatures (initials etc.). The scope of research was restricted, however. To research this medieval monument, more extensive archaeological excavations would be needed, including the whole site of the building. The origins of the chapel are the least known issue. The main question is why the west and east walls feature differently profiled foundations? Are the eastern foundations related to some more ancient (unconstructed?) building?