rondovaulted or arched roof, as seen from below
rondo noun "a vaulted or arched roof, as seen from below" (and usually not visible from outside); "a (large) hall or chamber so roofed", "vaulted hall" (WJ:414; VT39:9; in the Etymologies, stem ROD, the gloss is simply "cave" or "roof"; see VT46:12 for the latter gloss). Cf. *Elerondo.
n. vaulted or arched roof, vaulted hall; cave