Ray Cooper and Jimmy Merner from England.Our tour was excellent.Our guide gave a superb talk,in fact she never really stopped talking only to answer questions.She made the tour interesting and at times very amusing.I am an amateur historian and learnt many things I didnt know.The flak tower is amazing and the work done by the Unterwelten organization to clear the rubble and to mke it available to the public is only just short of a miracle.Please keep up the good work.If I have a crtiticism it would be the books for sale are only in German which is a pity as some of them I would liked to have purchased.Hopefully this will be remedied soon.Overall 10/10 We come to Berlin every year and will certainly do more underground tours.One tip to all on this tour wear warm clothes,thankfully we did but others in shorts and T shirts wish they had.When they say it will be 10 degrees they mean it.Dont miss this tour.