This resemble a Pellitory (Parietaria sp.) in the Nettle Family (Urticaceae). Pellitories commonly grow in wall and sidewalk cracks. What is unusual is that the common weedy species, Judean Pellitory (P. judaica), usually has more sharply pointed leaves, but this could be another species, or just an unusual form.
If the original poster is willing and able to reply after five years (!), perhaps s/he could tell us where the plant was photographed.