How many letters does the top answer for “rectangular paving stone with curved top; once used to make roads” have?

The most common answer is cobble (6 letters).

Crossword clue: rectangular paving stone with curved top; once used to make roads

3 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

cobble 6 letters wn-def

rectangular paving stone with curved top; once used to make roads

cobblestone 11 letters wn-def

rectangular paving stone with curved top; once used to make roads

sett 4 letters wn-def

rectangular paving stone with curved top; once used to make roads