The William H.G. FitzGerald Tennis Center is a public tennis center located in Rock Creek Park in Washington, D.C. It is named after William H. G. FitzGerald , a Washington-based private investor who was active in philanthropies and served as United States Ambassador to Ireland . It houses 15 hard courts and 10 clay courts. There are also five indoors courts which are heated and available in winter. The main stadium seats 7,500 spectators. The center is the home of the Citi Open , an annual ATP World Tour and WTA Tour event.