Acts 2:2

2. It was the apostles, then, and they alone, who were assembled together: (2) "And suddenly there came a sound out of heaven, as of a rushing mighty wind, and it filled all the house where they were sitting." What house this was has been variously conjectured; but the supposition of Olshausen, that it was one of the thirty spacious rooms around the temple court, described by Josephus and called oikoi, houses, is most agreeable to all the facts. Wherever it was, the crowd described below gathered about them, and this required more space than any private house would afford, especially the upper room where the apostles had been lodging.