Ruoms is a quaint little town on the Ardèche, where that river issues from between parallel walls of lias, not of great elevation, laid in regular horizontal beds. The road follows the river upwards for a short way only, and then turns up the Ligne towards Argentière. Ruoms was a walled town, and a considerable portion of the fortifications remains enclosing the church, old houses, and narrow and dirty lanes. The church is interesting, very early and rude Romanesque, lofty, with three bays and side aisles. There are quasi-transepts, not extending beyond the aisles. The east end is square. The piers and arches are unmoulded. A curious feature is a window on the south, apparently to serve for a clerestory light, with pilasters and sculptured capitals, but it has never been pierced through, so that it acts merely as a relieving arcade in the wall. Another unusual feature is that the wall of the south aisle has in it narrow square-headed lights in recesses under relieving arches. The tower has a zigzag ornament above the bell windows in black lava alternating with white limestone. The Ardèche is joined below the town by the river of La Beaume, that flows through a cañon very similar to that through which the Ardèche itself has run before it reaches the bridge of Ruoms. These cañons through the lias are curious rather than picturesque, the strata lie horizontally as regularly disposed as stones in an artificial wall. On the high ground some way up the Beaume, on the plateau, or _gras_, is the _aven_ or pot-hole of Réméjadou, twenty-five feet in diameter and eighty feet deep. One can hear the rush of water below, and this issues from the rock in the spring of Bourbouillet, two miles off, with sufficient volume to turn a mill. M. Janet says:— "This _aven_ has water flowing in its depths, filling the entire bottom. This stream issues from an arcade on one side about eighteen feet high, and disappears under a similar arch. It flows from north to south, which agrees with what the shepherd of Bourbouillet asserted, that this subterranean stream issues at the spring of that name. According to him, the inhabitants of Bourbouillet were much surprised one day to see the water of this spring charged with sawdust, and the explanation of the phenomenon was obtained only some days later, when they ascertained that some woodcutters who had been sawing up a good deal of timber had ridded themselves of the sawdust by throwing it into the _aven_."[7] This pot-hole was explored in 1892 by M. Gaupillat, and he established the curious fact that the underground stream enters and leaves the _aven_ by natural syphons, and not through galleries, so that it is not possible to track the stream up or down.