Penghu is not one island — it is an archipelago of roughly 90 landmasses scattered across a section of the Taiwan Strait where the sea is shallow, the winds are persistent, and the currents do not cooperate with ferry schedules. Siyu Island, in the southwestern reaches of the group, was among the outer islands most dependent on irregular water crossings to reach the county seat at Magong.

Connecting Siyu to Baisha Main Island by road would mean crossing the Roaring Gate Channel: a passage defined by its reefs, its speed, and its seasonal ferocity. The northeast monsoon hits Penghu with particular force in autumn and winter, churning the channel into conditions that make even experienced boat operators cautious. A bridge over this water would need to be built for the worst the Taiwan Strait could offer.

Work began in 1965. The engineers dealt with the underwater reef system by designing around it rather than through it. The construction stretched across five years, concluding on 25 December 1970, when the completed bridge opened to traffic.

The original structure was 2,478 meters long and 5.1 meters wide — enough for single-lane traffic to move between the islands. For more than a decade it held. Then salt air and sea wind began their slow campaign against the structure. By 1984, erosion and partial collapse required a significant expansion. The bridge was widened and strengthened, emerging from renovation as a two-lane road 2,494 meters long and 13 meters wide. On 1 January 1996, it was formally re-inaugurated in its expanded form. Seven emergency spaces are spaced along the route for vehicles in difficulty — a practical acknowledgment that crossing this stretch of open water, even on a road, is not without its hazards.

There are few places in Taiwan where you are more exposed to the island's relationship with the sea than in the middle of the Penghu Great Bridge. The deck runs at low elevation over open water, with Siyu Island visible in one direction and Baisha in the other, and nothing between you and the Taiwan Strait horizon but a guardrail.

In calm weather, the water below is shallow enough to show its colors: the pale greens of the reef system, the deeper blues of the channel, the white churn where currents meet. In winter, when the northeast monsoon is at full force, the bridge absorbs wind that has been building for hundreds of miles. Cars slow. Motorcyclists, a primary mode of transport on the flat Penghu islands, take the crossing carefully. The bridge is part of daily life for residents of Siyu, the thread that makes the outer island part of the county's road network.

The Penghu Great Bridge carries another distinction: it is one of the more visually arresting spans in Taiwan, precisely because of what surrounds it. There are no mountains to frame it, no river valley to cross. It sits in open water, connecting two low-lying islands in an archipelago that sits almost exactly at sea level, under a sky that the lack of terrain leaves completely unobstructed.

From above, the bridge's line across the channel is unmistakable — a thin ruled stroke connecting two pieces of land across blue water. It has become a symbol of Penghu's hard-won connectivity, the infrastructure that turned an island chain into something more coherent than a scatter of isolated communities.