Complex sentence: It begins in downtown Beverly Hills by Santa Monica Boulevard and ends at Alameda Street in Downtown Los Angeles, although east of Alameda, it becomes Fourth Street, where it heads to East Los Angeles, where it turns back into 3rd Street upon crossing Indiana Street.
Split into simpler sentences: It begins in downtown Beverly Hills by Santa Monica Boulevard and ends at Alameda Street in Downtown Los Angeles. East of Alameda it becomes Fourth Street, where it heads to East Los Angeles, where it turns back into 3rd Street upon crossing Indiana Street.