# Let's go in Spanish: vayamos vs vamos vs vamonos?

I understand that "Let's go" in Spanish is vamonos or vamos depending on the context. However, I have also learned from grammar books that all the "let's..." constructs translate into Spanish using the 1st person plural subjunctive conjugation. That's how we get platiquemos (from platicar) for "let's talk" and andemos (from andar) for "let's walk." By that analogy, shouldn't "let's go" translate into vayamos? Even the first person plural imperative of ir is vayamos. Why do we use vamos then?