Isolated, gigantic tin clusters of 58 atoms are discovered in the ternary compound Ba16Na204-Sn-310 {cubic, F43m, Z = 1, a = 26.2041(8) Angstrom) made by direct fusion of the elements at 800 degreesC. The cluster, made of four face-fused pentagonal dodecahedra, has 36 pentagonal faces and 90 edges, and resembles a concave fullerene "dented" at four places. It is made of three- and four-bonded tin atoms and is "stuffed" with four barium cations, [Ba-4@Sn-56](36)-. This is the largest main group naked cluster in the solid state besides the fullerenes. Also occurring in the structure are two other isolated clusters of tin, Sn16-n (n = O, 1, 2, 3, or 4) and Sn-B.