E-W running tufo and basalt wall (rubble and roughly worked faced blocks) filling construction cut 4049, which cuts N side of exterior wall 4050 of circular structure. Abuts interior wall of circular structure 4051. Top and W end of wall not fully exposed in 2011. Photographed and shot in, but to be photomodeled and more fully documented in 2012, when fully exposed. Relationship between wall and tufo paving 4041 to E and basalt paving 4048 to W to be determined.