Roedd yn ddiwrnod poeth a heulog yng ngogledd Cymru, ond roedd gan Gwilym syniad gwahanol ar gyfer eu diwrnod.

It was a hot and sunny day in North Cymru, but Gwilym had a different idea for their day.

Roedd Carys eisiau treulio'r diwrnod ar y traeth, gyda’r tonnau'n chwalu'n garedig ar y tywod.

Carys wanted to spend the day on the beach, with the waves gently crashing onto the sand.

Ond roedd Gwilym, wrth ei fodd â hanes, wedi siarad am ffrind newydd — Bwncer Dirgel o'r Oes oer.

But Gwilym, who loved history, had been talking about a new friend — a Secret Bunker from the old era.

"Pam ein bod ni yma, Gwilym?" cododd Carys ei llais ychydig wrthi'n edrych ar yr allt sy'n arwain at y bwncer.

"Why are we here, Gwilym?" Carys raised her voice a little as she looked at the hill leading to the bunker.

"Bydd yn gyffrous iawn, Carys! Mae'n lle rydym ni'n gallu gweld ein hanes o'r tu fewn." Atebodd Gwilym, gyda disgleirdeb yn ei lygaid.

"It'll be very exciting, Carys! It's a place where we can see our history from the inside," responded Gwilym, with a sparkle in his eyes.

Wrth iddyn nhw gyrraedd y bwncer, roedd y lle'n dywyll ac yn oer.

When they reached the bunker, the place was dark and cold.

Roedd hynny'n cyferbynnu'n llwyr â'r haul cynnes y tu allan.

It was completely opposite to the warm sun outside.

Roedd yr aer yn arogli'n hen, fel petaech mewn hen storfa.

The air smelled old, as if you were in an old storage room.

Wrth grwydro'r coridorau cul, clywsant y sŵn eu traed yn atseinio ar y llawr concrid.

As they wandered the narrow corridors, they heard the sound of their footsteps echo on the concrete floor.

Roedd Carys dal yn ansicr am y cyfan.

Carys was still unsure about it all.

"Gwilym," meddai gydag ochenaid, "pam mae angen i ni gasglu cyflenwadau hyn?"

"Gwilym," she said with a sigh, "why do we need to gather these supplies?"

"Ar gyfer y dyfodol, Carys. Os bydd diwrnod gwael yn dod, mae'n dda cael cyflenwadau wrth law," esboniodd Gwilym.

"For the future, Carys. If a bad day comes, it's good to have supplies on hand," Gwilym explained.

Roedd ei lais yn llawn o sicrwydd.

His voice was full of certainty.

Ar ôl ychydig o amser, deallodd Carys fod rhywbeth arbennig yn y bwncer hwn.

After a while, Carys realized there was something special about this bunker.

Ceisiodd blethu ei ffordd drwodd gyda Gwilym yn ei arwain i mewn i ystafell gudd.

She tried to weave her way through with Gwilym leading her into a hidden room.

Roedd yno arteffact rhyfedd, wedi'i orchuddio â llwch.

There was a strange artifact there, covered in dust.

Roedd yn edrych fel hen allwedd hir.

It looked like an old long key.

"Tybed beth mae hon yn ei datgloi?" meddai Carys, gyda chwilfrydedd yn ei llygaid am y tro cyntaf.

"I wonder what this unlocks?" said Carys, with curiosity in her eyes for the first time.

Gwenaodd Gwilym.

Gwilym smiled.

Pan ddaethon nhw allan, roedd y byd y tu allan yn dal i fod yn gynnes ac yn fywiog, ond roedd rhywbeth wedi newid.

When they came out, the world outside was still warm and lively, but something had changed.

Roedd Carys yn teimlo cynhesrwydd newydd tuag at antur Gwilym.

Carys felt a new warmth towards Gwilym's adventure.

Gwibiodd am yn ôl i'r car, yrru gan y mynyddoedd ac i lawr i'r dyffryn, ond â gwen ar ei hwyneb.

She darted back to the car, driving past the mountains and down into the valley, but with a smile on her face.

Roedd y bwncer dirgel hwnnw yn rhywbeth mwy na hanes; roedd hefyd gyfle i Carys weld y byd trwy lygaid Gwilym.

That secret bunker was more than history; it was also an opportunity for Carys to see the world through Gwilym's eyes.

Roedd yn haf newydd wedi gwir, ac roedd anturiaethau'n aros am eu tro.

It was indeed a new summer, and adventures were waiting for their turn.

Roedd eu perthynas wedi symud gam ymlaen, gyda chariad o deimlo'r dirgel a'r hen effeithiau.

Their relationship had moved a step forward, with a love for feeling the mystery and the ancient artifacts.