custom field related to another custom post type and mark more locations on map

1)
For example, I have two custom post types: places and events.
I would like to add a custom field to “add event page” that allows the user to select which “places” the event will be held. This is useful when the event is available in several places (or even just one place) which can be chosen from the “places” database. Basically, I want to use the custom post type database as a custom field in another custom post type. Is this possible?

2)
I would like to mark on the map several locations that are associated with an event, which is a custom post type. It will be great if I can even create a route on the map itself.