Yes, One Life to Live did a long storyline of an underground world called Eterna, back in 1989.
Per Wikipedia:
OLTL took a turn towards
science fiction in early 1989 as, through Michael Grande's machinations, Viki and several others (including Tina, Cord, Gabrielle and several others) were trapped in the underground city of Eterna. Alone with Viki in the underground city, Roger Gordon finally confessed his long-buried secret: He was raised in Eterna but had found a way to escape. He met Viki when she was in high school. They made love. One day, Viki watched in horror as the entrance to Eterna exploded. Believing that Roger was dead, she turned into Niki Smith. Viki/Niki gave birth to his daughter, Megan. She had carried the baby as Niki, then later turned back to Viki during childbirth, but Victor had her hypnotized to forget the birth. He then paid Roger to take the baby and leave town. Viki was amazed to learn that Megan, who had been her adversary, was actually her flesh and blood. While in Eterna, Viki and Roger's old feelings for each other began to resurface. Led by Clint, the authorities located and rescued everyone trapped inside just before Eterna collapsed.
They also did a time-travel storyline in 1988:
In 1988, Clint was blinded by a gunshot wound to the head. After a riding accident in the Arizona desert, he regained his sight but found himself transported back in time to 1888, and the old west town "Buchanan City". While there, Clint met the lookalike ancestors of Asa, Cord and Viki (played by Carey, Loprieno and Slezak respectively.) Like "Heaven", this storyline was intended to have a vague ending – after its resolution, Clint would reappear in the present and not be able to determine if he was actually there or had an extended hallucination. Before the storyline was finished though, the
Writers Guild of America went on strike. Several
scab writers rewrote the storyline so that Viki also went back in time to rescue Clint (who was on the verge of marrying her ancestor Ginny Fletcher at the time). Thus, the time-travel story was definitely established as a "real" event in the history of
OLTL.