Giant’s __; Northern Ireland’s Volcanic Path

Word Meaning:

CAUSEWAY — A road that is raised so as to be above water, marshland, and similar low-lying obstacles, which in some cases may flood periodically (e.g. due to tides). Originally causeways were much like dykes, generally pierced to let water through, whereas many modern causeways are more like bridges or viaducts.

Definitions from Wiktionary.