どこか行こうか。

The phrase 'どこか行こうか' is a combination of several Japanese linguistic elements. 'どこか' (dokoka) means 'somewhere' or 'anywhere'. It is formed by combining 'どこ' (doko), meaning 'where', with the particle 'か' (ka), which can indicate indefiniteness or questioning. '行こう' (ikou) is the volitional form of the verb '行く' (iku), meaning 'to go'. The volitional form expresses an intention, a suggestion, or an invitation. Finally, the particle 'か' (ka) at the end of the sentence turns the statement into a question, making it a gentle suggestion or an inquiry about the other person's willingness. Therefore, the complete phrase literally translates to something like 'Somewhere, shall we go?', which naturally conveys the meaning of 'Shall we go somewhere together?' or 'How about we go somewhere?'.