“Castellammare del Golfo” is the modern name for the ancient “Emporium Segestanorum” (Emporium of Segesta), and is located east of Eryx and north of Segesta.
The name used by Greek authors is "Emporion", that is a “town of maritime trade” . The "emporium" of Castellammare in Sicily was one of the clearest monuments to the opulence and extensive commerce of Segesta. Several ancient authors wrote on this trading port of the Elymi - for example, it was mentioned by Strabo (64 BC-19 AD), Ptolemy (100-175 AD), and Diodorus (90-27 BC):
“ […] This emporium seems to have grown up in the days of Strabo to be a more important place than Segesta itself, but the continued existence of the ancient city is attested both by Pliny (23-79 AD) and Ptolemy and we learn from the former that the inhabitants, though they no longer retained their position of nominal independence, enjoyed the privileges of Latin citizenship .
...It seems, however, to have been a decaying place, and no trace of it is subsequently found in history. The site is said to have been finally abandoned as a consequence of the ravages of the Saracens, in A. D. 900 , and is now wholly desolate ; but the town of ‘Castel a Mare’, about 6 miles distant, occupies almost, if not precisely, the same site as the ancient emporium or port of Segesta" .
Thanks to trade and its port, Segesta, according to Cicero (106-43 BC) was a sought-after territory by the Roman aristocracy, for which a cultivated field was worth about 6000 sesterces .
Another peculiar feature of “Castellammare del Golfo” in ancient times were the baths. Strabo said that “Sicily has hot springs in many places, among which those of Selinunte and Hymera are salty, while Segesta has drinkable water".
According to some critics these hot springs were also called "Aquae Perticianenses" or "Pincianae”, and presumably they were located in the ancient “Emporium”. On this issue a scientific debate has arisen because, according to some critics, they were situated at Selinunte. Although the issue remains uncertain, some scholars are inclined to place the famous "Aquae Pincianae" in the 'Emporium Segestanorum”: “It is true that the location of Aquae Perticianenses is unknown.
It has been suggested that Aquae Perticianenses is another name of for Aquae Segestanae (…). Perhaps Aquae Perticianenses is located at Castellammare del Golfo?” .The Paulys Real-Encyclopädie is of this opinion, which speaks of "Aquae Perticianenses or Segestanae or Pincianae.” 
The Romans were lovers of the thermal waters, and they built spas throughout the Empire. The use of such baths is of Greek origin, but because the Romans had a cult for the Greek traditions, that use over time was engaged by the Roman culture. The hydro-therapy among the Ancients was of almost sacrid value, founded on the concept of physical "purification", but also on the metaphysical concept of "purification of the soul."
The methods of using the baths were tied to very strict health regulations, consisting of alternating a cold with a warm bath. The spas were characterized by some important hygienic criteria, that is, by a cubicle called an "apodyterium," a room prepared for the cold bath - the so-called "frigidarium", a communicating room, that is the "tepidarium" and finally the room for a hot bath (the ‘calidarium’). The room used for the sauna was called "Laconicum" which means "Spartan," a term that emphasized the Greek origin of the spa.
The sauna was a means of therapy which enjoyed great prestige among the Romans, since the treatment was recommended by physicians such as Celsus (25 Bc-50 AD) and Galen (129-216 AD), according to whom the sauna not only stimulated sweating but also the circulation of the blood.
The waters of the Bath of Segesta flow at a temperature of about 46 degrees and they are very rich in hydrogen sulphide. The local spas implement mud-therapy and also hyper-thermal baths in swimming pools. The therapeutic indications pertain to diseases of the musculoskeletal system and rheumatoid arthritis - moreover, the thermal therapy is also indicated for skin diseases, and diseases of the respiratory tract .
"Castellammare del Golfo" is the Italian translation of the Late Latin expression “Castrum ad Mare de Gulfo”, that, after the splendours of antiquity, suffered a kind of oblivion, at least until the Arab times. In the Middle Ages spas fell into disuse, presumably for reasons related to the fact that they were considered a "pagan" habit and also (and especially) because of the lack of a sufficient wholesome way of life.
The "Castrum ad mare de Gulfo" is a name that lasted a long time, and it was “attested in the sources for centuries (…) until the adoption of the modern “Castellammare del Golfo” name (F. Maurici).
According to F. Maurici, the town was “completely omitted by historical sources until Al Idrisi, who mentioned the port, spa and fortress, called in Arabic al-Madarig ('Le Scale' = The Stairs)" .
The Arabs built a fortress here, which was later reinforced in Norman times. The castle was originally surrounded by the sea on three sides and connected to the mainland by a drawbridge, which was then rebuilt in brick between the 18th and 19th century. Ruins of the oldest structure, later incorporated in other walls, are still visible which allow us to assume that the original structure had polygonal bastions, and the crenellated walls of the village leaning directly on the castle.
These bastions were enhanced on the northern side by a low cylindrical tower that was probably built around 1537. It was here that the residential areas were found, characterized by large balconies. A cylindrical tower with an internal staircase allows access to the upper terrace. The castle is accessible from town by a stone bridge which crosses the ancient moat cut into the rock.
Over the centuries, the “castrum ad mare” and the village around it belonged to various local lords and it began to develop further under the Aragonese. Frederick II of Aragon (1272-1337) was designated Lord of the town (Frederick of Antioch), who, however, betrayed them, by selling out to the French.
In fact, according to the pro-Aragonese chronicler Michele Piazza, Frederick of Antioch: “on the side of King Robert of Anjou (1277-1343)] (...) continually he pressed him, day and night, with many sophistic arguments to convince the Angevin king to send his army in Sicily" 
Then the fortress belonged to Robert of Anjou, and later to Peter II of Aragon (1304-1342), who in 1336 gave it to Raymond of Peralla and his descendants.
King Martin (1356-1410) in 1399 gave the city to John Perollo, and then it returned to the Peralla family whose members were the Lords of Castellammare del Golfo at the beginning of the 15th century. It then passed to Peter Spadafora and Ruffo, Sigismondo de Luna (died 1530) and finally to Baldassarre Naselli (17th century) .
See also Castellammare del Golfo for a detailed travel and visitor guide
1. See G.B. Pellegrini, “Toponomastica italiana …”, Hoepli, 1990, p. 82
2. Strab. I.; Plin. III. 8. s. 14; Ptol. III, 4. Paragraph 15.
3. Amico, ad Fazell. Sic. VII. 4. not. 9
4. See Sir W. Smith, “Dictionary of Greek and Roman Geography”, 1857, p.949
5. "In Verrem", III, 49
6. See Gerald Verbrugghe, “Sicilia”, 1976, pp. 71 ff.
7. See Paulys Real-Encyclopädie der classischen Altertumswissenschaft: neue Bearbeitung, J. B. Metzler, 1963, p. XXXVII. See also Forcellini [ “Totius latinitatis lexicon opera et studio Aegidii Forcellini …”, 1867, p. 392: “Aquae [waters] Segestanae aut Pincianae, in Sicilia hodie [today] Castellam[m]are”].
8. On these aspects of the Bath of Segesta, See the important and detailed essay by L.M. Bonica Santamaria, “Il Termalismo in Sicilia”, in “Archivio storico siciliano”, Messina, 2001, 82, pp. 17-84
9. See S. Tramontana, “Gli anni del Vespro …”, Dedalo , 1989, p. 270
10. See M. Amico-G. Di Marzo,”Dizionario topografico della Sicilia”, 1855, Vol. I. p. 258
11. See F. Maurici, “Sicilia bizantina …”, In “Atti quarte giornate di studi sull’area elima”, 2003, p. 902