Vietnam has the Red River delta in the north, the Mekong delta in the south, and a narrower central coastal region backed by mountains. The long S-shaped mainland and the change in width between these regions are more useful than rice fields alone.
Two deltas beside a mountainous spine
Compare the Mekong delta with the central coast. Notice how much farther the lowlands extend inland in the delta.
Similar landscapes across borders
Cambodia shares the Mekong lowlands, while southern China shares some northern landscapes. A close crop of paddy fields can be ambiguous. Determine whether the surrounding terrain fits a delta or a narrow coast.