 Eruvin 14a, b)

The symbolism of the brazen sea is described in detail in the Midrash Tadshe.The sea represented the world; the ten ells of diameter corresponded to the ten Sefirot; and it was round at the top (according to the Talmud passage above cited) as the heavens are round.The depth of the sea was five ells, corresponding to the distance of five hundred years' journey between heaven and earth (compare Chagigah 13a).