LongconsideredanuglyNazirelic，ahalf—destroyedconcretefor-tressinBerlinnowhasbecomeanadditiontotheGermancapital’Stour-istmap.SinceAprilregularguidedtourshavetakencuriousvisitorsintothevastWorldWar11structuretOseetheturretinteriorsandtheeffectoftwofailedattemptstoblowitupafterthewar.ItisapartofagrowingtrendinGermanytoshowabroaderviewoftheWarandincludeGermansufferingafteryearsofsoleattentiontotheevilsoftheNazis.TourspassthickwallsthatresistedbombsandRussianartillery，barehallsandstaircaseswhereciviliansshelteredanddeepshaftswhichCar—fledanti——aircraftshellsfromthebasementtotherooftopgunssevenfloorsabove.Visitorscanalsomarvelattechnologywelladvancedforitstime.Thegunsteering，forexample，wasfullyautomated.Aradartower300yardsawaytrackedenemyaircraftandfedsignalsalongcablesstillvisi—bleclingingtothewalls.ThefortressiSoneofsixthatAdolfHitlerorderedtobebuiltintheGermancapitaltodefenditfromairattack.HiscommandinSeptember1940camejustdaysafterBerlincameunderathree—hourbarragefromAlliedplanes.Financialconstraintseventuallylimitedthenumbertothreefortres—ses，completedbyApril1942，althoughtwofurtherstructureswerebuiltinHamburgandVienna.Eachcomplexcouldholdaround15，000civiliansandtheir8foot一6-inchwallsweredeemedimpenetrable.Thepost——warAlliedoccupiersinBerlindecidedtodestroymostmilitarystructures.TheBritishandRussiansmanagedtobringdowntwoofthecomplexesafterseveralfailedattempts.However，theFrenchwereunabletodestroythefortressintheirnorthernBerlinsector，leavingtwotowersand1.6millioncubicyardsofdebris.Thelatterwaspartlylandscaped，buttheremainingstructurehasbeenlargelyuntouchedfor50years.TheBerlinUnderworldsAssociationalreadynanstoursofnearbywartimeandColdWarshelters，butpreparingthehalf—demolishedairdefensefortressforvisitorswasataskofadifferentorder.Ittookthou—sandsofhoursofvolunteerlabortoreadythebuildingforshow.ThebunkersmaynotbeSOwellvisitedastheglassdomeontheReichstag，Germany’Sparliamentbuilding，butinterestisgrowing.Lastiyear25，000visitedthesitecomparedto8，000in2001.