If you want to stretch your whole body, work on your strength and be at mediative inversion, master your downward facing dog. Ado mukha svanasana. It is probably the most famous yoga pose of all. I call it the everything yoga pose, trying to say all in one (English is not my first language:)
It is a bitter sweet pose. Some days it feels like I couldn't hold more than a few seconds in it and some days it feels so restful and so weightless. After all these years I still feel like my whole practice is going towards mastering downward facing dog.
So, it is still a journey but there are few things that can help make the journey more fun.
I like to focus on each part of the body, upper and lower, to be more specific arms and legs.
Before going in the pose, I like to practice the external rotation of the arms since it is so unfamiliar to most of us, walking most of the day with droopy shoulders, the yoga class is a nice place to remind our bones where they should be placed.
grab a block or simply open the palms of your hand so both pinkies will face each other, straighten your arms and start lifting them while they're straight. Keep the palms open and notice when your palms starting to close down, get back to the position where they were open and breath 3 slow deep breaths. Repeat 3 times.
Now, place the palms on the floor remember the rotation of the arms and maintain it while coming in your downward facing dog, keep the breath slow and deep as you take your sitting bones up and back, keep your knees bent and stretch your arms longer.
Here, practice the internal rotation of your thighs, feel how the sitting bones are spreading apart.
when you feel comfortable in that, you can slowly start straightening your legs.
Master that and you'll find ease.