You will discover, on five levels, all the interior rooms which have been reconstructed down to the smallest detail: engine rooms, filter rooms flanking casemates, chamber, infirmary, armory, radio transmission room, observation post equipped with a powerful telemeter which will allow you to observe the bay of the Seine within a radius of 40 km as well as a room dedicated to the largest construction site of the 20th century which mobilized, for 3 years, more than 2 million workers.