Fourth Dimension 326 S Myrtle Ave, Monrovia, CA91016 Fourth Dimension is a nightclub and billiard hall located right in the heart of Old Town Monrovia on historic Myrtle…More Avenue. It features two floors and two bars with a dance floor that is often packed. Music ranges from rock to disco to Latin to alternative rock to rhythm and blues. There are 31 pool tables, several pinball machines, an arcade and a patio. The clientele consists mostly of young 20-somethings. On Sundays, Mondays and Wednesdays the age limit is 18 and older.