A lyre stone is a bifurcated megalith with a central tenon – in the form of a lyre – characteristic of Senegambia, which is given an astronomical role. The lyre stone also has a symbolic value: in 1967, the Senegal Post issued a stamp dedicated to the lyre stone of Kaffrine. It has also been chosen as the logo of the Directorate of Cultural Heritage of Senegal.
In 1985, 47 bifid stones were identified by Guy Thilmans, three of which left their original site (those of Keur Ali Ngane, Soto and Djigui). The first is in one of the rooms of the Historical Museum of Senegal in Goree, the second at the Quai Branly Museum in Paris, the third in Dakar. Of the 44 stones left on the site, nine are on the Wanar site, including three on the same front line of a megalithic circle – which is exceptional. But many are damaged.
At the musée du quai Branly, a stone more than 4 tons and a weight of 4 tons marks the entrance of visitors in the space dedicated to Africa. It comes from the village of Soto, located 5 km southwest of Kaffrine, 250 km from Dakar, on the Tambacounda line. Unlike most similar megaliths, grouped in circles, this stone, ferruginous sandstone or laterite, was half-sunken in the ground and isolated. It is considered one of the oldest megaliths in the world. Owned by the State of Senegal (IFAN), it has been deposited at the former Museum of African and Oceanic Arts, as part of a protocol for the exchange of works of art signed at Dakar on May 31, 1967. In return, a number of Aubusson tapestries were loaned to the Republic of Senegal.