It is now thousands of years since the Churban Bais HaMikdash. Many Jews feel very comfortable in their surroundings. How can a person help themselves visualize and understand the great loss of the Bais HaMikdash?
I don't think one can visualize the churban bais hamikdash without a change in life and perspective. However, I did hear of a summer camp, which had the kids build forts and other buildings, and then on Tisha B'av the counselors burned it all down, and deestroyed it. This apparently helped the kids gain an appreciation of the feelings of loss with the temple.
For myself, I have found that I regret the lack of beis hamikdash more than I used to. I can attribute this change in perspective to 4 activities.
- Reading the Chumash closely with minimal commentary. Ask yourself how what you are reading applies to your life today. (So you can understand why the temple is important in the first place)
- Buying model beis hamikdashes and building/destroying them every year. / having pictues of the beis hamikdash around you.
- Paying attention to the words in davening related to David's reign, returning to Israel, and the karbonot, and asking myself if I truly believe what I am praying or if I am making a mockery of it. If I am making a mockery of it, why do I continue? (Warning, such line of thinking might make you seriously consider making aliyah)
- Seriously follow the rules during the year which relate to not having a beis hamikdash. (i.e. the rules that apply all year long, not just the three weeks)
I think it helps to study mishnayos or g'mara (Midos, Tamid, Yoma, P'sachim, perhaps others) about the avoda and miracles in the bes hamikdash. (Likewise, the musafos ("yotz'ros" of musaf) of Yom Kipur.) It gives one a feel for what's missing. Reading the ArtScroll kinos helps one focus on the loss and gives an idea of the difference that the churban made and has made. (I happen to have read parts of ArtScroll's kinos, whereas I haven't read other commentaries. Doubtless others are good for this, too.)
I think the one way to truly appreciate what was lost is not to get bogged down in the ritual aspect of the Beis Hamikdash itself. Korbanos are very hard to relate to in a non-agrarian society. Instead I would focus on what the Beis Hamikdash represented, ie a physical manifestation of the presence of God and a place where a person can connect directly to him.
Some people today complain that their davening lacks enthusiasm, or that they just don't know what God wants from them. Imagine being able to go to a place where you could bring God a present and watch as a fiery lion descended from heaven to consume it. What kind of Shmonei Esrei would you have then?
But these are only mental exercises; to visualize them more completely I would suggest augmenting them with tangibles. If you live in Israel that is pretty easy. Otherwise I would suggest finding online materials, maybe imagery from the arch of Titus, or even simply reading aloud some of the ma'amarei chazal (such as the story of the mother and her 7 sons who perished).
I think you will find that when you start with a strong mental and emotional underpinning, the visuals will have a much stronger impact.