When I asked where this place was located, I was pleased to learn it was located right across from the Courtyard hotel on Penn Ave. Il Tetto is on the third floor, part of a three restaurant complex.
There is a small elevator located on the first floor that you use to reach the roof top. Upstairs, you will find a open airy bar. At the time I went (December) the glass roof was closed, but still allowed natural light in.
The bar is long with plenty of seats. Also, they have a number of large tables that seat 8 or more. The have a diverse, varied craft beer menu. I went with the Alpine Double Hoppines, which was outstanding.
Give this place a chance.