both as a naval base and military base dun beal gallimhe offered several advantages. it was surrounded to the north by a number of small islands that, separated from the dun by large streams and extremely boggy ground, made physical progress difficult and an attack futile. to the south it was bounded by muddy estuary flats and the effects of the tide which made approach from this side just as difficult. the dun itself was raised at the very end of a thin peninsula of land that could withstand attack by a relatively small number of defenders. due west was the river, which is one of the fastest-flowing in europe, and yet almost the only ford on the river. if all was lost, defenders could withdraw to the west bank and flee into iar connacht. if, however, the attacking force could still not make the east bank, there were only two other routes to the other side, neither favourable: one was to risk a crossing of lough corrib, which however can be treacherous at the best of times to an unskilled sailor; second, the unenviable sixty mile slog north to cong.