Bryn Celli Ddu's passage is roughly aligned with sunrise at which event?

Bryn Celli Ddu’s passage is roughly aligned with sunrise at the summer solstice.

The passage at this Neolithic monument points toward the midsummer rising Sun. Around the summer solstice, sunlight can travel down the passage and illuminate the interior of the burial chamber, including a quartz-rich stone at the rear. That alignment is why the site is often discussed alongside prehistoric monuments with astronomical connections.

The interpretation has a long history. In 1906, astronomer Norman Lockyer argued that Bryn Celli Ddu marked the summer solstice, although the idea was initially ridiculed. Later investigations renewed interest in the alignment, and archaeologist Steve Burrow has supported the case for a midsummer sunrise orientation.

The answer is not the winter solstice: that association is more famously linked with monuments such as Newgrange in Ireland and Maeshowe in Orkney. “Summer solstice” is the best choice here, although the exact intentions of the Neolithic builders cannot be proved with complete certainty.