adj.
1) ~ to + inf. (it would be ~ to build a house so close to the river)
2) ~ that + clause (it is ~ that they would even make such an offer)
UNTHINKABLE
Meaning of UNTHINKABLE in English
The Bbi combinatory dictionary of English, a guide to word combinations. Комбинаторный словарь английского языка Bbi. Руководство по словосочетаниям. 2012