You barely notice it as you fly by on I-44, and you may hardly care while stuck at the traffic light at Grand and Russell. But nestled within winding, scenic walkways, discreetly tucked into an earthen sheath, is the Compton Hill Reservoir. The original stone-lined reserve, completed in 1870, had an appearance that was more lake than holding tank. Its 86-million-gallon capacity eventually was eclipsed by the 100-million-gallon capacity of the Stacy Park facility, but nothing could replace its ambiance. In fact, with the help of its water-lily ponds and fountain, the reservoir was a favorite stop during the 1904 World's Fair. Vertical walls were erected in 1917, splitting the reservoir into two tanks. By 1931, concrete pillars had also been added, and a roof was in place. The reservoir stayed in this configuration for more than a half-century, acting as a direct feed to the low-pressure zone in the waterworks system. But by 1995, time had taken its toll. The structure had become particularly susceptible to earthquake damage, and the roof was near collapse. Plus, an inefficient pipe layout resulted in the reservoir's draining almost as soon as it was filled, often causing "stale water" and low pressure. In July 1996, renovation began by taking the southern half off-line. Seven hundred tons of fill was laid to raise the floor 17 feet, resulting in better head pressure. Two smaller tanks -- a mere 14.3-million-gallon capacity each -- were built on this new bed, near what had been the center of the much larger original tanks. Each new tank is made of "precast, wire-wound, prestressed concrete," incorporating some 2.3 million pounds of reinforcing steel and 619 miles of wire. As massive as that sounds, the leaner reserve's distance from the streets still keeps it unassuming as ever. By 1999 the reservoir was back in full service, quietly dispensing water into the distribution system -- the perennially green backdrop to midday strolls and lazy picnics on an otherwise gently sloping hill.