Taken literally your question is about post to post relationships. Bad news — WordPress core doesn’t do post to post relationships. However there are some solutions ranging from frameworks like Posts 2 Posts to plugins like Post Connector.
Stepping a bit back though, structure you are describing strongly implies grouping of posts. The mechanism for such in WP is custom taxonomies (core taxonomies being categories and tags for example).
If you create Place and Activity as taxonomies then you get pretty much everything out of the box — from UI in post editor to archives and querying. The only limitation would be just how much info you want to cram into individual place/activity items (terms of taxonomy). They aren’t to be intended as content heavy as posts and many less tools focus on enabling complex data for them.
Related Posts:
- How to get all taxonomies of a post type?
- How do I append multiple taxonomies to the URL?
- Custom taxonomy not showing up when adding a new custom post type
- How do I list custom taxonomy terms without the links?
- How to list custom taxonomy categories?
- Custom Taxonomy Template Post List with Sort Order
- wp_insert_term doesn’t work with custom post type’s taxonomy
- How to list all categories and tags in a page?
- Taxonomy archives based on Custom Post Type
- Create an archive page for custom taxonomies
- Get the ‘slug’ of a custom taxonomy
- Custom Metabox with Taxonomy Dropdown – Saving Issue
- How to get the parent’s taxonomy?
- Include custom post type in “all posts”
- How do I list terms of a custom taxonomy at i.e. domain.com/brands/
- wp_insert_post custom taxonomy
- Taxonomy-{taxnonomy}.php is not working
- Display taxonomy term only if there’s a value
- Get list of terms of current taxonomy archive for another taxonomy
- Get all taxonomies for all post types
- Associate Taxonomies Across Post Types
- Linking three taxonomies with ACF
- Show Post Count of a Category
- Order WordPress Custom Taxonomy Pages & Pagination Not Working
- Relationship between two taxonomies and a custom post type [closed]
- Menu Multiple Taxonomies
- How to make a custom taxonomy selectable in post publish area?
- Problem with custom post types, taxonomy and permalinks
- How to create new category for custom post type?
- Fetch taxonomies by custom post type id array
- get_terms showing all categories instead of the ones assigned to a specific post
- Custom page template for category taxonomy
- How do I get array of types associated with a taxonomy?
- wp_set_object_terms() not adding new term to custom post and custom taxonomy
- Display all posts in main category and 1 subcategory
- wp_get_post_terms on custom post type with custom taxonomies returning an empty array
- Categories of custom taxonomy don’t show any posts
- How to display custom taxonomies with links in filter menu?
- Custom Taxonomy back-end customizations
- How to Filter custom post type by taxonomy?
- Is it possible to have dedicated page for parent/child taxonomy?
- Why are taxonomy terms not saving when using custom meta boxes with radio button taxonomy selectors?
- Display a grid of taxonomy terms at root taxonomy page
- limit value taxonomy based on previous taxonomy value wordpress
- How to conditionally redirect to the post from a taxonomy page?
- How do I display the grand child items of a taxonomy term?
- Is it better to use WordPress Custom Post Types or Taxonomies?
- How to make custom taxonomy into drop down select in a custom metabox
- How do I share categories across multiple post types?
- How to Set Taxonomy Object Description?
- Custom Taxonomy Is Being Pulled into a Page, But It Doesn’t Have A Hyperlink
- Querying two taxonomies with tax_query not woking
- Hide specific taxonomies from a taxonomy list using ‘get_object_taxonomies’
- Custom taxonomy (categories) on custom post type return no results
- Variable not working in WP_Query
- get_category_link() for custom post type does not include custom slug rewrite?
- Targeting categories in custom fields
- Alphabetically sort a taxonomy.php template by post title
- Custom Post Types not queried in Custom Taxonomy archives or Native archives
- Show Taxonomies with admin area for custom post type?
- Rewrite custom post type with taxonomy
- My custom taxonomy is only displaying 1 of 3 terms
- Changing CPT slug and taxonomy already registered in parent theme
- Copy/Move selected taxonomy terms to another taxonomy for posts
- Custom Taxonomy Terms in Menu lead to which page?
- Get posts by category name
- Query Custom Post Type by Taxonomy
- “Menu order” being ignored when querying posts from a parent taxonomy with “include_children” set to true
- How can i display a taxonomy? i have created a plugin and then a custom type. and a taxonomy , also i have register it
- How to order taxonomy terms by most recent post?
- Custom taxonomy returns 404 even with saving permalinks
- Create custom post type categories
- How to add CSS class field in Custom Taxonomy?
- Change custom post taxonomy values from front-end
- Set a Default CPT taxonomy by taxonomy id
- List all posts associated under custom taxonomy
- How to Use A Custom Post Type as Taxonomy for Another Custom Post Type
- How to manage a dynamic multi-level page hierearchy system?
- Categories manage
- Add other all taxonomies as meta boxes to custom post type
- How to get post type archive category title
- Pages of my taxonomy terms are showing all posts
- Custom post type category link + add to menu
- Single taxonomy for different custom post types
- Changing an item in drop down after 5 latest posts per taxonomy
- Filter Term By Parent Term – Custom Post Type
- Best approach to allow front-end display of posts’ reviewers?
- Custom Post Type and Taxonomies, creating the corresponding template file and loop the data
- How to create TEMPLATES for TAXONOMIES? What I have to change in this code?
- List all posts from custom post type by taxonomy
- Displaying taxonomy icon outside archive page
- Connecting multiple post types? Or linking “News” posts with “Game” posts how?
- Sort by Custom Post Type (Multiple Loop)
- Archive templates based on taxonomies
- How to display elements of different post types?
- How to display only taxonomies of custom post type in a page?
- get_the_term_list() wanting to loop through the returned values
- Get all active posts that are tied to a custom taxonomy for a custom post type
- Taxonomy term archive claims there are no posts, but there are. How to resolve?
- How to list custom taxonomy terms without the hyperlinks?