AddPersonPlacesAndPeoplePlaces.rb

class AddPersonPlacesAndPeoplePlaces < ActiveRecord::Migration
  def change
    create_table :people do |t|
      t.string :name
      t.timestamps
    end

    create_table :places do |t|
      t.string :name
      t.timestamps
    end

    create_table :people_places do |t|
      t.references :person, index: true
      t.references :place, index: true
    end
  end
end

Person.rb

class Person < ActiveRecord::Base
  has_many :people_places
  has_many :places, through: :people_places
end

PersonPlace.rb

class PersonPlace < ActiveRecord::Base
  self.table_name = "people_places"
  belongs_to :person
  belongs_to :place
end

Place.rb

class Place < ActiveRecord::Base
  has_many :people_places
  has_many :people, through: :people_places
end