Mae'n noson haf braf yng Nghaerdydd, yn ystod Gŵyl Ganol Haf.

It is a fine summer evening in Caerdydd, during the Gŵyl Ganol Haf.

Mae'r strydoedd yn llawn pobl, cerddoriaeth a golau.

The streets are full of people, music, and light.

Ond oddi tano, mewn hen seleri Castell Caerdydd, mae Gareth, Carys a Llewelyn yn mynd ar antur.

But beneath, in the old cellars of Castell Caerdydd, Gareth, Carys, and Llewelyn are embarking on an adventure.

"Rwyt ti'n sicr na fyddwn ni'n cael trafferth i ddod allan eto?

"Are you sure we won't have trouble getting out again?"

" gofynnodd Llewelyn, ei lygaid yn llydan wrth edrych ar fap yr ardal.

asked Llewelyn, his eyes wide as he looked at the map of the area.

Gwenodd Gareth, yn llawn hyder.

Gareth smiled, full of confidence.

"Peidiwch â phoeni, Llewelyn.

"Don't worry, Llewelyn.

Bydd yn gyfle i ddarganfod rhywbeth newydd!

It will be an opportunity to discover something new!"

" Meddyliodd Gareth am Carys wrth ei ochr, gan obeithio y byddai hi'n gweld ei ddewrder.

Gareth thought about Carys next to him, hoping she would see his bravery.

Roedd Carys yn edrych o gwmpas, ei llygaid yn peillio â chyfrieth.

Carys was looking around, her eyes sparkling with intrigue.

"Mae'n swnio’n gyffrous," meddai, er ei bod hi'n ansicr a ddylai hi ddilyn Gareth mor frwd.

"It sounds exciting," she said, though she was unsure if she should follow Gareth so eagerly.

Teithion nhw trwy'r twneli, a'r waliau lleidiog yn atseinio gyda sain eu camau traed.

They traveled through the tunnels, the damp walls echoing with the sound of their footsteps.

Roedd y teimlad o hanes ac antur yn llenwi'r awyr o'u cwmpas.

The feeling of history and adventure filled the air around them.

Ond wrth iddynt fynd ymhellach, dechreuodd eu fflachlampau fflachio, a'r map yn llai defnyddiol na'r disgwyl.

But as they went further, their flashlights began to flicker, and the map was less useful than expected.

"Wyt ti'n siŵr bod hyn yn syniad da?

"Are you sure this is a good idea?"

" Llewelyn oedd yn ceisio dal ei nerth.

Llewelyn was trying to hold his composure.

Roedd ganddo fraw o ofodau caeedig, er mwyn iddo geisio cuddio hynny.

He had a fear of confined spaces, though he tried to hide it.

"Dim ond ychydig ymhellach," meddai Gareth, yn benderfynol.

"Just a little further," said Gareth, determined.

Roedd Carys yn edrych ar Llewelyn, yn teimlo ei ansicrwydd.

Carys looked at Llewelyn, feeling his uncertainty.

Daethant at groesffordd yn y twneli.

They came to a crossroads in the tunnels.

"Rhaid i ni benderfynu," meddai Carys.

"We have to decide," said Carys.

"Dewch!

"Come on!"

" gwaeddodd Gareth, yn rhai ar gyfer y llwybr culaf.

shouted Gareth, choosing the narrowest path.

Ond Llewelyn gorfu a stopiodd.

But Llewelyn hesitated and stopped.

"Na, rhaid i ni fynd yn ôl!

"No, we have to go back!"

" Roedd ei lais yn llawn ofn a dicter.

His voice was full of fear and anger.

Fe wnaeth yr ymladd.

There was an argument.

Datgelodd Gareth ei dyhead i wneud Carys falch ohono, a Llewelyn datgelodd ei ofnau, tra roedd Carys yn gofyn iddynt i beidio a tharo ar ei gilydd.

Gareth revealed his desire to make Carys proud of him, and Llewelyn revealed his fears, while Carys asked them not to fight.

Yn y pen draw, gwrandawodd Gareth.

In the end, Gareth listened.

"Mae'n iawn," meddai, yn rhedeg â llaw ar y cefn Llewelyn.

"It's okay," he said, running a hand on Llewelyn's back.

"Peidiwn â mynd yn bellach.

"Let's not go any further."

"Symudon nhw'n ôl, nes iddynt sylwi ar ddrysau hen ystafell.

They moved back until they noticed the doors of an old room.

Agorodd Carys y drws a dod o hyd i ystafell gudd, wedi ei llenwi gyda hen atgofion o'r wyl.

Carys opened the door and found a hidden room filled with old memories of the festival.

Canfyddon nhw rhywbeth arbennig, rhywbeth na welwyd ers blynyddoedd.

They discovered something special, something unseen for years.

"Mae'n wych," meddai Llewelyn, yn gwenu gyda rhyddhad.

"It's amazing," said Llewelyn, smiling with relief.

Roeddent wedi dod o hyd i dir cyffredin, ac roedd hyn wedi caledu eu cyfeillgarwch.

They had found common ground, and it had strengthened their friendship.

Deallodd Gareth nad oedd yfaeth o arddangos mewn perygl yn bwysicach na diogelwch y grŵp.

Gareth realized that putting the group in danger to show off was not more important than their safety.

Roedd Carys yn gwerthfawrogi ysbryd anturus Gareth, a Llewelyn falch ei fod wedi dal i fynd ymlaen.

Carys appreciated Gareth's adventurous spirit, and Llewelyn was proud he had continued on.

Wrth iddynt gerdded allan o'r selerau, roedd golau gŵyl yn disgleirio yn y pellter, ac roedd Carys, Gareth a Llewelyn yn gwybod eu bod wedi creu atgof fyddai'n aros gyda nhw bob amser.

As they walked out of the cellars, the festival lights were shining in the distance, and Carys, Gareth, and Llewelyn knew they had created a memory that would stay with them always.

Mae cyfeillgarwch yn dod â mwy o werth na'r antur mwyaf dirgel.

Friendship holds more value than the most mysterious adventure.