"You know, we’re not far from the Leaky Cauldron here, it’s only in Charing Cross—"
-- Ron Weasley while on the run in Tottenham Court Road (DH9)
Located in central London, Charing Cross Road is the site of the Muggle side of the Leaky Cauldron, and therefore borders Diagon Alley as well. Harry walked down Charing Cross Road with Hagrid (PS5), and later rode down it on the Knight Bus (PA3) and in Ministry cars (HBP6).
Charing Cross Road is a busy commercial street known for its book shops toward the south end and music stores toward the north. Notably, there is no parking along Charing Cross Road, which begs the question of where the Ministry cars parked while waiting for Harry and the Weasleys to finish their shopping in Diagon Alley (HBP6).
From the Web
Charing Cross Road on Wikipedia