In San Francisco if you start from St. Mary's: UCSF is 1.1 miles away by car, CPMC Davies is 1.5. If you start at Kaiser's Geary campus: UCSF Mt. Zion is 0.4 miles away, St. Mary's is 1.1 miles away. If you start at SF General: St Luke's and UCSF Children's Hospital are 1.5 miles away – although UCSF only takes pediatric patients and I think Sutter closed the ER at St Luke's because focusing on specialists is more profitable.

In Oakland: Kaiser and Summit ERs are about half a mile from each other and UCSF Children's Hospital is about 1.5 miles away.

Lower Manhattan: Mt Sinai Beth Israel and Bellevue are about a mile away and there's a VA hospital with an ER next to Bellevue.

In Chicago: UI and county are 0.6 miles away by car and Rush is on the other side about 0.4 miles away. UI actually calls this the "Illinois Medical District".

In Seattle: Swedish First Hill and Virginia Mason are 0.4 miles apart. Kindred's right there too but doesn't have an emergency department. UW Harborview does have an ED and is 0.4 miles in the other direction.

Houston?

Atlanta, Boston, Houston, and Philadelphia all have medical center areas with 3+ hospitals within walking distance of each other.

Houston has the largest medical center in the world with ~10 including Texas Children's Hospital, the largest children's hospital in the world (or at least it was a couple of years ago).

Philly has 4+ hospitals in center city (Jefferson, Penn), 7+ in university city (Drexel, Penn, CHOP), and a smattering more all over. Baltimore had 3+ hospitals near downtown but I think most got absorbed into UMMS, so it's Hopkins and UMMS, but lots of different facilities around.

Boston's Longwood Medical area is a great example of a place you can stand and be within a mile of 4 hospitals. Brigham and Women's, Boston Children's, Beth Israel and New England Baptist.

3 of the 4 are Harvard Medical School affiliated and our outstanding hospitals.

oh, i didn't mention this isn't america, but instead a third world backwater country