1 8 6 9 , ▁replacing ▁a ▁nearby ▁station ▁of ▁ 1 8 4 0 ). ▁They ▁are ▁located ▁just ▁outside ▁opposite ▁ends ▁of ▁the ▁Pent agon ▁– ▁an ▁area ▁within ▁the ▁ring ▁roads ▁which ▁follow ▁the ▁boundary ▁of ▁the ▁old ▁city ▁walls . ▁Short ly ▁after ▁opening , ▁both ▁stations ▁were ▁handling ▁large ▁volumes ▁of ▁comm uter , ▁regional ▁and ▁international ▁passengers , ▁but ▁through ▁jour ne ys ▁required ▁dis emb ark ing ▁and ▁a ▁street - level ▁transfer ▁through ▁the ▁city ' s ▁old ▁town , ▁a ▁distance ▁of ▁over ▁. ▁ ▁The ▁idea ▁of ▁an ▁under ground ▁railway ▁line ▁linking ▁the ▁two ▁stations ▁was ▁first ▁suggested ▁in ▁the ▁ 1 8 6 0 s ▁as ▁part ▁of ▁a ▁proposal ▁for ▁the ▁covering ▁of ▁the ▁S enne . ▁That ▁proposal ▁was ▁never ▁implemented . ▁The ▁current ▁version ▁was ▁planned ▁before ▁World ▁War ▁II , ▁after ▁a ▁decision ▁originally ▁made ▁in ▁ 1 9 0 9 , ▁and ▁it ▁came ▁into ▁service ▁on ▁ 5 ▁October ▁ 1 9 5 2 . ▁Both ▁stations ▁were ▁demol ished ▁and ▁re construct ed ▁to ▁allow ▁through ▁services , ▁re open ing ▁in ▁ 1 9 5 2 . ▁ ▁Three ▁new ▁intermediate ▁stations ▁were ▁constructed ▁along ▁the ▁route ▁to ▁serve ▁the ▁city ▁centre . ▁Two ▁of ▁them , ▁Br uss els ▁Chap el ▁and ▁Br uss els ▁Congress , ▁were ▁intended ▁stops ▁only ▁for ▁local ▁comm uter ▁services ▁and ▁have ▁never ▁been ▁heavily ▁used . ▁The ▁largest ▁of ▁the ▁new ▁stations , ▁Br uss