The clayey and sandy 'terra forte' soil refers to degradation of basalt and obsidian and does not contain any pumice (soki soki); this is a rich type of soil that confers power and structure to the Zibibbo grapes. As a wine, 'Terra Forte' is therefore the antithesis of 'Soki Soki' – viscous, age-worthy and tannic "come un vino rosso!", this is a class act with flavors of bergamot, mandarin, and peach skin bitters. The grapes come from a single vineyard in the contrada Bonsulton (neighbouring Bukkuram), from vines planted in 1931. Winemaking involves 15 days of maceration on skins, and ageing occurs in glass demijohns as well as stainless steel vats. Only 1,000 bottles are produced each year.