But what makes Trôo especially interesting is that the whole height is like a sponge, perforated with passages giving access to halls, some of which are circular, and into store-chambers; and most of the houses are wholly or in part underground. The caves that are inhabited are staged one above another, some reached by stairs that are little better than ladders, and the subterranean passages leading from them form a labyrinth within the bowels of the hill, and run in superposed storeys. In one that I entered was an oven, with a well at its side. A little further, in a large hall, a circular hole in the floor unfenced gave access by rope or ladder to a lower range of galleries. Any one exploring by the feeble light of a single candle, without a guide, might be precipitated down this abyss without knowing that there was a gaping opening before him. A long ascending passage, with niches in the sides for lamps, leads to where the fibres of the roots of the trees on the mound above have penetrated and are hanging down. It is said that the gallery led on to the castle, but since this latter has been ruined it has been blocked. In the holes whence flints have dropped spiders harbour, that feed on ghostly moths which flit in the pitch darkness, and when caught between the fingers resolve themselves into a trace of silver dust. But on what did these spectral moths feed? A pallid boy of sixteen who guided me about the town told me that he had been born in a cave; that he slept in one every night, and worked underground all day. His large brown eyes could see objects in the dark where all was of inky blackness to me. It is astonishing with what unconcern mites of children romp and ramble through these corridors, where there is danger not only on account of pitfalls, but also of the roof falling in. Where I went, guided by a child of ten, every now and then I was warned-- "Prenez garde, c'est écroulé." The town--it was a town once, but now contains 783 inhabitants only--is partly built at the foot of the bluff, but very few houses are without excavated chambers, store-places or stables. The café looks ordinary enough, but enter, and you find yourself in a dungeon. There is but one street--La Grande Rue--and that has space and landscape on one side, and houses built against and into the rock on the other. A notice at the entrance to the street warns that no heavy traffic, not much above the weight of a perambulator, is permitted to pass along it, for the roadway runs over the tops of houses. A waggon might crash through into the chamber of a bedridden beldame, and a motor be precipitated downwards to salt the soup of a wife stirring it for her husband's supper. At Trôo chimneys bristle everywhere, making the hill resemble a pin-cushion or a piece of larded veal. There are in the depth of the hill wells, and to these mothers fearlessly despatch their children to fill a pitcher, as often as not without a light.