The nymphaeum is one of the quieter pieces of ancient Myra, overshadowed by the rock tombs and theatre but part of the same Lycian-Roman cityscape. It helps round out the site, showing that Myra was not only a dramatic necropolis but a functioning urban place with water, public architecture, and civic display.
Do not make a separate journey for the nymphaeum alone. Look for it while visiting Myra's main ruins from Demre, and let it add texture between the headline sights.