Standard spelling using 大 and kana for かがり, with 火 for 'fire'.
大篝火
Full kanji spelling using 篝 (a non-jōyō kanji); less common in modern writing.
Etymology
Compound of 大 (おお, 'big') + かがり火 (かがりび, 'bonfire'). The word かがり火 itself derives from かがり (連用形 of verb かがる, 'to stitch' or 'to build a fire') + 火 (ひ, 'fire').