My particular mainstreet was 7th Avenue and I used to watch the dancers through the glass at The Metropole Cafe. It was originally a jazz club that operated in New York from the mid-1950s through 1965 when it switched to a topless gogo bar. They then painted the front window black leaving a small circular opening through which you could watch the dancers who were up behind the bar.
You can see the progression from club to Topless GoGo bar below.
So turn out the light lay your head back and go down to Mainstreet.