Complex sentence: Seven Dials is a small but well-known road junction in the West End of London near Covent Garden where seven streets converge to form a roundabout, at the centre of which is a pillar bearing six (not seven) sundials.
Split into simpler sentences: Seven Dials is a small but well-known road junction in the West End of London near Covent Garden where seven streets converge. At the centre of the roughly circular space is a pillar bearing six (not seven) sundials.