I occasionally send my butler down to the wine cellar during a meal to fetch more wine. The cellar is arranged as a three-dimensional grid of wine barrels. Which rows and columns of the grid do I need to check for leavened food before Passover, to verify there's nothing that was left behind absent-mindedly by the butler?
Q: Must a person search for Chametz in his wine cellar in his home?
A: If he (or his butler) occasionally goes there to bring wine to the table, and it is therefore possible that some Chametz had been brought there, he must search the top two layers of bottles in the first row one encounters upon entering the cellar (Shulchan Aruch 433:9, Mishna Berura 433:40).
Although the reference quoted uses the word "bottles", the source uses the word "חָבִיּוֹת" which means barrels.
מַרְתֵּף שֶׁמְּסֻדָּרִין בּוֹ שׁוּרוֹת שֶׁל חָבִיּוֹת זוֹ אֵצֶל זוֹ עַד שֶׁנִּתְמַלֵּא כֻּלּוֹ, וְחוֹזְרִין וּמְסַדְּרִין שׁוּרוֹת אֲחֵרוֹת עַל הַתַּחְתּוֹנוֹת עַד הַקּוֹרָה, אֵין צָרִיךְ לִבְדֹּק אֶלָּא שׁוּרָה הַעֶלְיוֹנָה וְאַחֶרֶת לְמַטָּה מִמֶּנָּה; דְּהַיְנוּ שׁוּרָה עַל פְּנֵי רֹחַב הַמַּרְתֵּף, וְלֹא עַל כָּל שֶׁטַח הַמַּרְתֵּף אֶלָּא עֶלְיוֹנָה הָרוֹאָה אֶת הַקּוֹרָה וְאֶת הַפֶּתַח, וְאַחֶרֶת לְמַטָּה מִמֶּנָּה