The interlude between the 6th and 7th trumpet continues with the testimony of the two witnesses. Two was the minimum number of witnesses needed to convict a person (under Jewish law someone could not be convicted on the word of a single eye witness). The two are representative of the entire church and the testimony of the church to an oppressive and unjust world. Notice that they have prophetic authority. Moses and Elijah were the greatest of the Old Testament prophets. Elijah called fire from heaven and stopped the rain; Moses sent plagues and turned water into blood -- the same authority given to the two witnesses. The city in question (8) is most likely Jerusalem although it could be a wider metaphor for Rome.
The critical element in this chapter is a reality check. The church is called to live by certain values. These values will clash with the prevalent values of the world around it. We are called by our Lord to stand against sin and injustice. We are called to a different understanding of wealth and power. We stand with the powerless, the broken and the downtrodden. Part of our call is not to pass judgment on the people of the world (that is God's responsibility) but to be a living critique of the values, mores and behaviors of the world around us. This behavior did not make Jesus popular and it will often times have us at odds with the world around us. The church must build bridges into that greater community while at the same time remembering that we follow a different code than that larger community.
The witnesses suffer persecution are murdered and are denied burial (a grave and shameful treatment in the ancient world) but are finally called to heaven. Some scholars work to identify who these two witness are (or were or will be). Most scholars agree that the two witnesses are symbolic of the church as a whole.
Notice the second woe is passed -- the third woe is coming very soon (14). The third woe is never recorded in Revelation. It is left hanging as a reminder that the cycle described here will be ongoing until the end of time.
The seventh trumpet is sounded and the end of chapter 11 is a summary of the rest of the book. The reign of Christ is announced and this leads to worship and the revealing of the Ark of the Covenant (the ancient symbol of God's presence with his people).