The Grado Peninsula was already famous long before Venice was even founded. Its origins, along with those of nearby Aquileia, date back to Roman times:

Historical map
The name Grado is derived from the Latin word *grado* (meaning "step"), which leads historians to conclude that there was once a pier with a harbor there. Or perhaps it alludes to the favorable geographical conditions:
Julius Caesar's fleet already took advantage of the two typical winds of the Adriatic - the cool, dry bora from the northeast and the warm, humid sirocco from the southeast - thanks to which, depending on the season, one could sail from Grado in one direction or the other.
The pier was part of the large port system of Aquileia, as it was possible to navigate the Natisone River upstream from Grado all the way to Aquileia. Numerous Roman finds, such as the foundation of a structure beneath the 4th-century basilica (a must-see!) on Piazza della Vittoria, attest to Grado's economic importance under the Romans.
During the Migration Period and the invasion of the Huns under Attila, the population of Aquileia fled with their bishop to the Grado lagoon. This marked the city's birth. While Aquileia gradually fell into ruin and slipped into insignificance, Grado assumed its original role. Over the centuries, however, the city lost its former significance, and after the fall of the Venetian Republic, it became a rather insignificant fishing village with barely more than 2,000 inhabitants, passing to the Habsburg Empire as part of the Principality of Gorizia and Gradisca.
Kiss my hand!
In 1892, Emperor Franz Joseph granted Grado the title of "spa town." This marked the beginning of its rise as the most popular spa destination for Austrians on the northern Adriatic coast. Yet even as the Austrian monarchy came to an end, Grado managed to maintain its status as a spa town.
Its geographical location gives Grado a mild Mediterranean climate with ionized sea air and sand rich in minerals.
Just recently, there has been a welcome wave of renovations in Grado; the thermal baths now offer a wide range of medical services under the attentive supervision of qualified specialists.
Today, wellness is a top priority in Grado, not to mention rehabilitation therapy and beauty treatments for body and mind.