Just a few kilometers to the east of the busy city of Petah Tikva are the remains of the ancient city of Afek. Located at a geographically strategic position, the city was an important fortress as well as sitting on top of one of Israel's most important water resources - a resource that is still vital today. The springs around Afek form the source of the Yarkon River. In ancient times the Yarkon was a natural barrier along the region's main highway, the Via Maris (the Coastal Route). Caravans crossing Israel from north to south had to pass through a gap between the springs and the mountains, and the ancient Afek pass controlled the entire Via Maris. The source of the springs is the rain which falls on the Judean Mountains to the east and finds its way down westward-inclined impervious rock until it manages to bubble to the surface at Afek, due to a geographical rift. In ancient times the Yarkon River was a formidable obstacle to cross, but today most of this water is contained and the springs are part of the mountain aquifer - the most important and largest source of underground water in the country. Until about 10 years ago, the Yarkon River was merely a trickle and became a slow-running, sludge filled, poisonous, foul waterway. It had been used for the disposal of sewage and industrial waste. In 1997 dozens of Australian athletes fell into the river 12 kilometers downstream in Ramat Gan, when a footbridge they were crossing collapsed into the highly polluted river. Four athletes died after ingesting the putrid water. It was decided to radically revitalize the river and allow some fresh water once again to flow along its banks. Although the flow is nothing like it was during pre-State times, the river is now running more cleanly and today a number of breeds of fish and aquatic life have returned to the river. Tel Afek is located at the heart of the Yarkon National Park and is administered by the Israel Nature and National Parks Protection Authority. The 13,000-dunam (some 3,250 acres) park is a popular destination for locals and tourists throughout the year, but it is in the spring that it can be seen at its best. Because of the winter rains, two small lakes form at the park. The upper lake is formed from the rain run-off from the mountains to the east. As this lake fills, it overflows into a beautiful, meandering clear rivulet that makes its way gently down over shallow riffles to a lower lake, which is a holding area for the excess water that will eventually become part of the country's water resource. Wild flowers and animals abound in the park beneath the plentiful variety of trees as all enjoy the bounty of the water below. This time of the year, the lakes and rivulet have dried up after the winter rains gave way to hot, precipitation-free summers. Yet the park still attracts visitors who want to enjoy the revitalized Yarkon River by hiring a rowing boat, fishing, or just walking along its bank. The impressive archaeological remains have been subject to continuous excavation by the Tel Aviv Archaeological Institute, particular from 1976 to 1985. In the late Bronze Age (1300-700 BCE), the Egyptians established a fort to guard the road. Later, the Philistines located themselves there, fought the Israelites and captured the Ark of the Covenant (as recounted in Samuel, 1-4). King Herod rebuilt Afek in approximately 35 BCE and named the city Antipatris after his father Antipater. The apostle Paul was also said to have been brought there about 60 CE by the Romans on their way to Caesarea. The city was destroyed by an earthquake in 363 CE. The Crusaders also regarded the hill as being of strategic importance, and built a castle on it over the site of a Jewish fort originally built about 66 CE at the time of the First Jewish Revolt. They called it Migdal Afek (Tower of Afek). Today a 16th-century Turkish fort dominates the hill, a reminder of the continued strategic importance that has always been associated with the site.