Why is the transit of Venus so special?
First, planetary transits like this don't happen very often. The last transit of Venus was in 2004. The one previous was in the 1800s. The next one won't occur until 2117 and then again in 2125.
Second, transits like Venus allow scientists to study the sun in greater detail. In the 1800s and early 1900s, the transits were sought after events. One explorer made the trip to Tahiti to best view a transit of Venus in the 1700s. The transit viewings back then probably didn't help in measuring planetary distance as much as they thought. Primatative equipment and other atmospheric phenomena not known cast an even harder shadow on their results.
Still, you can imagine what it was like to see this hundreds of years ago when falling off the edge of the earth was considered modern scientific truth!
Edgewater Park in Cleveland is the place to be to properly view the transit of Venus. Never look directly as the sun! Download this map from NASA for more details http://eclipse.gsfc.nasa.gov/OH/tran/TOV2012-Fig02.pdf
The transit starts at 6:04PM and finished when the sun disappears below the horizon at roughly 8:55PM