Superheroes need to rest after a long battle with their greatest supervillains. Some heroes go home to their apartment or fancy house in order to store their suit until they are called to action again. Other heroes have secret lairs just for housing their superhero attire as well as provide other services they made need.
Whether it's containment, research, development, or simply a place for the hero to seclude and brood, there are a lot of these lairs in the DC universe with some being more iconic than others. These have to be actual lairs so casual homes such as Barry Allen's house or Wayne Manor will not be counted.
STAR Labs
The antithesis to LexCorp, STAR Labs has been the sanctum for several superheroes in the DC world including Cyborg, The Flash, and even Superman at times. STAR Labs are also a company that provides assistance for heroes in the form of technological gadgets or discovering the weakness of powerful metahuman villains.
Emil Hamilton tends to be the leader of STAR Labs and he has shown to be helpful by providing Superman with the means to combat weaknesses such as Kryptonite. In others, it's where The Flash's friends work by helping him in a fashion similar to Oracle.
The Quiver (Arrow Cave)
Every good superhero needs a lair, even if they have to rip off another hero's lair to have it. The Arrow Cave belongs to Green Arrow and his wife Black Canary. In some portrayals it looks akin to a fancy penthouse, in others it's an underground bunker, and it is a high-tech lair such as the CW version.
It does the job no matter what: a parking area for his vehicles, training courses with plenty of archery targets, and cases to hold the suit and arsenal of Green Arrow, Black Canary, and their sidekicks. In the Injustice comics, Harley Quinn gave a superior name: The Quiver rather than the Arrow Cave which makes it sound like an off-brand version of Batman's lair.
The Clock Tower
Though she is more famous for working with the Bat-Family, Barbara Gordon AKA Oracle or Batgirl also leads the Birds Of Prey as well as operates on her own. As a result, she has her own lair in the form of a clock tower in Gotham City. This became her main abode during her tenure as Oracle.
The Clock Tower features an advanced computer that can allow Barbara to tap or hack into any system on the planet. She also has a grand view of the city, and the innards of the clock tower provide a unique visual. In some versions such as the Arkhamverse, the Clock Tower can transform into an apartment for her to live in or provide a shelter for her allies.
Rock Of Eternity
This mystical cave acts as the sanctum for Shazam, containing thrones for the whole Shazamily, ancient artifacts that need protecting, and holds back the Seven Deadly Sins. It's a very cold and barren lair but one that features a lot of beautiful details, especially with the architecture.
There is more that can be found within the Rock Of Eternity such as doors to other realms, a train station that can transport passengers to the Magiclands, and more depending on the incarnation and story.
Titans Tower
Subtlety is not the Titans' strong suit consider the design of their layer is a skyscraper in the form of a giant T. That said, the Titans Tower remains an iconic staple of the characters housing everyone from multiple versions of Robin to Cyborg to Superboy.
Over many decades, Titans Tower has seen many designs: in others, it's a simple skyscraper while others have done for more fantastical designs. The interior is one of the more appealing lairs with a good mix of superhero elements that also comes across as a perfect place for teens and young adults to live in.
The Hall Of Justice
The Justice League wasn't all that subtle at first either with their original headquarters in the form of the Hall Of Justice. It is a giant building in the middle of Washington D.C. with the name plastered on it with the world publically knowing that the Justice League operates out of it.
Despite the silliness of the Hall, it remains a famous piece of DC history that fans still cherish and the mythos still uses every now and then. In the Young Justice animated series, the Hall Of Justice was just a public cover while the League truly operated out of a different secret lair. In the DC Extended Universe, Wayne Manor was going to act as the new Hall Of Justice.
Oa
Technically a whole planet should not count as a lair but since it is a planet meant to be the headquarters of the entire Green Lantern Corps, it still works. Whenever a Green Lantern of any sector is done with a case, they can either return to their homeworld or get some earned respite on the planet Oa.
With massive alien structures, jade buildings, and a plethora of galaxy protectors to relax with for some R&R, Oa is a paradise. That is at least until the next time an event causes some threat or powerful villain of the Green Lanterns to attack Oa.
The Fortress Of Solitude
Standing as one of the last remnants of Krypton, the Fortress Of Solitude is Superman's retreat in the Arctic. In some versions, it's simply a place for Superman to learn about his homeworld of Krypton or to mend his suit and body.
However, The Fortress Of Solitude has evolved into a powerful palace with Kryptonian computers and technology, a preservation area to protect endangered alien species, and access to the Phantom Zone. In the DCEU, it is portrayed less as a crystalline palace and was instead a Kryptonian scoutship. When Superman went evil in the Injustice comics, the Fortress Of Solitude becomes a vital part of Superman's Regime.
The Watchtower
Over time, the orbital space station known as the Watchtower has become the definitive lair for the Justice League. It makes sense, it orbits the Earth they protect, they are out of sight most of the time, and it's usually fitted with enough technology and protection that would make Cyborg blush.
Unlike the Hall Of Justice, the Watchtower tends to feature plenty of lodging for heroes to live in or recover in should they need to. This gives the Watchtower a more comforting presence whereas the Hall Of Justice was more akin to a place of business. For some characters such as the Martian Manhunter, the Watchtower acts as a home.
The Batcave
To likely nobody's surprise, the most iconic superhero lair is the Batcave. For decades, the Batcave has been the Bat-Family home and place of operations below the already extravagant Wayne Manor. Whether it's the creepy, cavern-like Batcave with minimal platforms or the massive underground structure with memorabilia of iconic villains, a hangar, and different rooms for different purposes, it works.
The Batcave has become as iconic as the Batmobile itself with fans looking forward to each new incarnation and how it is designed. Even adaptations from movies to animated television shows treat the Batcave with class and glamor with unique designs.