According to the archaeological catalogue of the town hall of Lalin (year 1999), these “mámoas” (tombs) formed part of a set of seven, known as “Mámoas da Cruz” (Mámoas of the Cross) which, nowadays, stay only three.
There are two more "mámoas" situated in a place known as " Zarra do Canal " which exist nowadays. All of them belong to the Neolithic and they were plundered, as the majority of the existing ones in Galicia, after the license granted by Philip III to “Vazquez de Orxas” in 1609. The aim was to recover the existing exchequers that were in tombs for the Royal Estate, though many of them were plundered by the peasants searching gold.
At "Mamoa da Cruz” (Cross tomb)" it is possible to appreciate perfectly a tomb of land and 5 mainstays that stand out of the chamber and the top stone. In this one, there is a hollow where, maybe, a cross could be fixed, hence its name. It was recognized by the department of Culture of “Xunta de Galicia” (Regional Government of Galicia) in 2011.
There is a closed enclosure formed by 7 mainstays with a great stone with two reduce in the shape of a circle, orientated towards the east. Neighbours know it with the name of “Altar do Sol”(Altar of de Sun). He was declared Site of Cultural Interest as historical artistic monument in 1974.
The “Mámoa do Cruce” (“Cross Mamoa”), call like that for being just at the entrance of Alperiz crossing, next to the road. The number of mainstays that exists today cannot be estimate with clarity. One of them stands out 1.5 meters up and it is possible to see in it an engraving in the form of a serpent, orientated to east.