Complex sentence: The Ashby BART station hosts a flea market each weekend in its parking lot, which attracts a regular large crowd of drummers and other musicians who play under the canopy of the BART station.
Split into simpler sentences: The Ashby BART station hosts a flea market each weekend in its parking lot. The flea market attracts a regular large crowd of drummers and other musicians who play under the canopy of the BART station.