The nearest Shinkansen stops are at Kakegawa, if you're coming in from the direction of Tokyo, or Hamamatsu if you're coming from the Nagoya area. From either, you can catch a regular JR train the rest of the way to Iwata Station.
Iwata Museum of Fragrance (磐田香りの博物館, Iwata Kaori no Hakubutsukan), Tatsuno 2019-15, ☎ +81 53 836-8891. 9:30am-5pm, closed Mondays. This unique museum explores the history and culture associated with fragrances in a variety of exhibits, including the "Experience Fragrance" exhibit which, for an additional fee of 2100 yen, allows visitors to create and bottle their own fragrance. A café allows visitors to try out various fragrant herbal teas. Adults 300, students 200, children 100.
Okegaya Marsh (桶ケ谷沼, Okegaya Numa), Iwai 315, ☎ +81 53 839-3022. 9am-5pm, closed Mondays. An almost 2 kilometer-long marsh and the surrounding park has abundant wildlife, including 67 species of dragonfly.
Toyooka Plum Park (豊岡梅公園, Toyooka Ume Kouen), Uenobu 1989-1, ☎ +81 53 962-2666. 9am-5pm. Over 4000 plums trees blossom in a beautiful valley here every spring. Adults 500, children 100.
[dead link]Yuya Wisteria (熊野の長藤, Yuya no Nagafuji), Ikeda 330, ☎ +81 53 836-9600. Meter long arms of wisteria hang from a frame which covers almost 600 square meters. Great picnic spot during the April-May bloom. A wisteria festival is held here during Golden Week as well. Free.
LaLa Port Iwata (ららぽーと磐田), 1200 Takamigaoka (off the Tomei Expressway north of the Iwata Interchange), ☎ +81 538-59-0100. 10AM-9PM. The newest and largest western-style mall in the area, with a wide variety of shops, restaurants, and a Toho Cinema. One unique store, Enshu no Eki, carries a vast array of food products made, grown, or caught in the Enshu (western Shizuoka) area.
[dead link]Choupana Iwata, Fukudenakajima776-1 (on rute 43), ☎ +81 538-58-2321. Sat.-Sun.12:00-24:00. Popular Brazilian all-you-can-eat rodizio with salad bar, rice and beans, salgados, feijoada and a wide selection of cuts served tableside, including various beef cuts, chicken, chicken hearts, lamb, and pork. ¥2000-3000. ¥2000-3000.
[dead link]Ajishou Tenhiro (味匠天宏), Mitsuke 3884-5 (about 2km north of JR Iwata station), ☎ +81 53-832-7078. 11am-2pm, 5pm-9pm. Tempura served in an old-style Japanese atmosphere. The restaurant is installed in a historic house once lived in by the head of the Akamatsu clan. Beyond tempura, the restaurant also specializes in the local "three-color curry" (miiro kare). Dinner for around 5000 yen..