First, the claim that all Kingdom Halls of Jehovah's Witnesses do not have windows is simply not true. While it is true that some Kingdom Halls do not have windows because of cost and for the sake of security, many Kingdom Halls do have windows. Generally, a Kingdom Hall is built without windows in areas which tend toward hate crimes and vandalism against houses of worship.
Also consider: If Jehovah's Witnesses really had so many things to hide, then why do they continually attempt to invite interested persons to attend meetings conducted inside Kingdom Halls? Their book Jehovah's Witnesses—Proclaimers of God's Kingdom correctly notes: "Jehovah's Witnesses are in no sense a secret society. Their Bible-based beliefs are fully explained in publications that are available to anyone. Additionally, they put forth special effort to invite the public to attend meetings to see and hear for themselves what takes place."
Jehovah's Witnesses invite all interested ones to attend meetings with them at their Kingdom Halls. Just contact your local Kingdom Hall for times.
From the Jehovah's Witnesses Official Media Web Site:
"Have you ever been curious about what goes on inside the houses of worship of Jehovah’s Witnesses?
"You don’t need to make a hole in the wall to find out about our services. All meetings are open to the public, and visitors are welcome.
"Usually a Kingdom Hall is a modest structure that has an auditorium with chairs for the audience, a speaker’s platform, a lectern, a library, and an area where members can request or pick up literature for Bible study.
"You won't see religious symbols such as crosses or images in a Kingdom Hall. Why not? We follow the Bible’s command: “Guard yourselves from idols.” So we don’t use religious images in our worship—1 John 5:21.
"We usually hold services two times a week, and most of the programs involve audience participation similar to a classroom discussion. Worship starts and ends with prayer, and services normally include singing. All services focus on reading and discussing the Bible and seeing how to apply it in one’s life. Those in attendance—even the very young—are encouraged to read the verses being discussed in their own copy of the Bible." (Read the Full Article.)
For more, see:
Kingdom Hall - Links to Information (Defend Jehovah's Witnesses)