The Equatorial is the hotel Rachel inherits from her dead husband. (Which dead husband? Oh, the third or fourth one, we lost count. Whatevs.)
Rachel works really hard—for once in her life—to make this hotel a success: "[Her] proudest achievement," she tells us, "is the swimming pool, patio, and gardens, which [she] put in entirely by [her]self" (5.9.7). By "herself," she means she paid a bunch of local men next to nothing, fired anyone she merely suspected might be stealing, and yelled at them all until the job got done.
Whew, bossiness works up quite a sweat.
We're tough on Rachel, but her job sounds a lot like the job of any manager—or president. She says, "It's like running a whole little country [...] You make something, seems like, and spend the rest of your days toiling so it won't go all unraveled" (6.1.6). Rachel's sin of choice has always been pride, so it's no surprise she has great pride in her hotel.
A single woman who grew up in the '60s running a hotel is a great achievement. However, this hotel pretty much symbolizes everything that's wrong with the way countries, especially African countries like the Congo, are run on the backs of abused workers, like the poor workmen who build the pool that she puts in "herself." To a lesser extent, it represents the world's economic injustices, not to mention what Leah calls Rachel's "standards of white supremacy" (5.11.5). (I.e., the hotel is for whites only.)
Of course, Rachel is completely oblivious to the fact that she's part of the problem: "These horrible things had nothing to do with us" (5.11.127), she says comfortably.
Uh, they have everything to do with her. The Equatorial, like the line of demarcation it is named after, is a bold line that divides the world.