Learn Dutch: Daar bouwen wij het kamp op. - There we set up the camp.

When referring to a location, the unstressed word is er. However, you cannot put a locative er in the first position of a sentence. To put 'there' at the front for emphasis, you must substitute it with the stressed form daar.

How does using Daar relate to the rules for avoiding a double er sequence?

If we changed het kamp to a quantity like 'two of them' (er twee), the sentence would be Daar bouwen wij er twee op. Because the locative 'there' was pushed to the front and substituted with daar, we avoid the illegal double-er sequence that would happen if we tried to use a locative er and a quantitative er together in the middle field.

Why is the word op sitting at the very end of the sentence?

The verb here is the separable verb opbouwen (to set up or build up). In a Dutch main clause, the conjugated part (bouwen) takes the second position, while the separable prefix (op) gets kicked to the very end of the clause.

Why is the word order bouwen wij instead of wij bouwen?