In 1973, Leo Kalantzakis opened a 24-hour coffee shop at the ground floor of 1203 Fannin (below a parking garage), where, according to the Houston Chronicle, "he'll offer platters of seafood, steaks cooked to order, specialty salads, and a magnificent sandwich selection. Two midnight breakfasts, steaks and the traditional ham 'n eggs are ranking high, says manager Jerry Erwin."
The signage looks big and gaudy and probably was outdated even by 1970s standards (certainly with energy requirements coming in soon) but the reason why Leo's can still be talked about today is a rather scathing report by Marvin Zindler's "Rat & Roach Report" from 1982. That's where the pictures in this post come from, the current A dingy downtown diner that never closes has issues, with health inspectors finding two dead mice in a storage area and "roaches crawling on the condiment cooler" (as Zindler relished the alliteration). By 1984 Leo's was gone.
The current site is now home to McCormick & Schmick's Seafood & Steaks; the building was demolished and rebuilt in the late 2000s.