I’ve been post­ing these on Face­book and despite their loose per­mis­sions pol­i­cy, you still can­not view my pro­file unless you are a mem­ber, so…

Every Fri­day I will post a pic­ture here that I’ve tak­en in my trav­els and ask you to iden­ti­fy some­thing about it.

This week we go under­ground. Do you rec­og­nize this for­ma­tion and where it is? Please do not give the answer but feel free to leave a com­ment that you do know. I’ll post the answer on Sun­day.