One of the oldest, most impressive (to me) structures along lower Euclid was this house, built 1833-34, was this home for Samuel and Cornelia Cowles at 622 Euclid -- yes, the site of the "missing tooth" between the 5th Street Arcades and the Residences at 668. This photo was taken in the 1850s (looks like it was drawn on to better show the washed-out rooflines)...
This photo is later than 1850's. At the time this was taken this was Ursuline College. It was purchased in 1850 by Bishop Rappe. The sisters added the third story and the wings to it. This is on the lot of the Residences at 668 the former Taylor and Sons department store. The "missing tooth" is where the Clarence Building stood. The Clarence building pre-dated the Taylor building.
For some reason I am not allowed to quote the picture, but I hope the text helps.