1. Proceedings for review may be instituted by filing a petition in the circuit court of the county of proper venue within thirty days after the mailing or delivery of the notice of the agency’s final decision.

2. Such petition may be filed without first seeking a rehearing, but in cases where agencies have authority to entertain motions for rehearing and such a motion is duly filed, the thirty-day period aforesaid shall run from the date of the delivery or mailing of notice of the agency’s decision on such motion. No summons shall issue in such case, but copies of the petition shall be delivered to the agency and to each party of record in the proceedings before the agency or to his attorney of record, or shall be mailed to the agency and to such party or his said attorney by registered mail, and proof of such delivery or mailing shall be filed in the case.

3. The venue of such cases shall, at the option of the plaintiff, be in the circuit court of Cole County or in the county of the plaintiff or of one of the plaintiff’s residence or if any plaintiff is a corporation, domestic or foreign, having a registered office or business office in this state, in the county of such registered office or business office, except that, in cases involving real property or improvements thereto, the venue shall be the circuit court of the county where such real property is located. The court in its discretion may permit other interested persons to intervene.