When it's OK to omit "where?" [duplicate]

Solution 1:

You can generally omit where when the head noun suggests a place:

 1a. This is the one of the few places [ where you can breathe real air. ]
 1b. This is the one of the few places [ you can breathe real air. ]

Here, the head noun is place, which of course suggests a place. However:

 2a. This is the web page [ where the claim was first made. ]
 2b. *This is the web page [ the claim was first made. ]

Example 2b is ungrammatical because web page is unlikely to suggest a place.

(Examples 2a and 2b are taken from "A Student's Introduction to English Grammar" by Huddleston and Pullum, page 185.)

In this answer, * marks a sentence as ungrammatical in standard English.