There aren't many designated trails within the boundaries of Goblin Valley State Park, but Goblin's Lair should be on the list for everyone who visits the area. There is a $13 day use fee assessed for entrance to the park.
First things first, stock up on water. The South end of the parking lot boasts the nicest bathrooms I have seen in a state park. Ever. White walls, heaters, sinks, mirrors, FLUSHING TOILETS. I felt like I was in an episode of Fixer Upper, the after-the-flip bathroom tour. Right outside these plush facilities there is a water spigot with potable water. Finding access to potable water when you're BLM camping in the desert is like pouring yourself lucky charms and only marshmallows fall into your bowl.
Once you've maxxed your water supply head to the North end of the parking lot. There are bathrooms here as well, but when comparing a vault toilet to the thrones previously mentioned, well, there's no comparison. The trail winds down the packed sand dunes and flattens out after the first quarter mile. There is no hiding from the sun on until you reach the lair itself so protect your skin under buckets of sunscreen and those funny floppy hats. Be sure to stay left at any forks in the trail, if you take the path on the right it will lead you to the Valley of Goblins. A fun place to play around but save that route for after you've completed your hike and you won't get lost amongst the formations.
The trail takes you alongside steep hoodoo topped cliffs on your right and flat prairie land on your left. We didn't encounter one human on the entirety of the 3.7 mile loop, which is listed as moderately trafficked, (help with transition) something we really appreciated when we got to the lair itself. The hike changes swiftly from a stroll through the desert to a moderately challenging but quick scree slope scramble. The photos below will give you an idea of what to look for, but there is no mistaking Goblin's Lair once you encounter it.
While it seems like a cavern of monstrous creatures, the lair is actually a slot canyon, the entrance of which has been sealed off by falling boulders. There are two access points to get yourself inside the canyon. Our route was the 'easier' of the two for the two dogs to hop down. If you, or your pups, aren't super agile I don't recommend climbing inside. Once we found a comfortable ledge with space for 4 bodies we spent a bit of time curled up on the rocks of the cavern, enjoying the cool of the space and the eerie ambiance. By the time we headed back to the car the shade of the massive hoodoos covered our trail. The entire trip took us about two hours, and if you don't find Goblin's Lair to be reason enough for the park entrance fee I can confirm the bathrooms are.