Where is the Ruler Tool Hiding in Photoshop CC 2015?

The Ruler Tool available in Photoshop 7 and Photoshop CS4 doesn't seem to want to be found in Photoshop CC 2015. While it is the tool I use almost as often as the Marquee tool, it seems to be some sort of an orphan, having moved between Photoshop 7 and CS4. Now has it vanished? Is there some default I don't know about? (In my opinion, many important software defaults are wrong.)