Beginning with the Astrodome in 1965, domed stadiums featured a fixed roof and temperature controlled environment. There is no natural light in these parks, necessitating use of the most distinguishing aspect of an indoor park: artificial turf. An important type of ballpark is the indoor park. These parks were covered with a fixed roof, usually a hard concrete dome. Reasons to build indoor parks were varied. The Astrodome, the first indoor sports stadium ever built, was built to escape the hot and very humid climate of Houston and the Kingdome was built to escape Seattle's constant rains. There is little to no natural light in these parks, necessitating the use of one of the most distinguishing aspects of an indoor park: artificial turf. Since there was not enough light to grow grass, artificial turf was installed, and this affected the game. Artificial turf was harder, and thus a ball hit on the ground moved faster and bounced high. This, coupled with the usually dull white or gray roofs that could camouflage a fly ball, caused what Twins fans called a "dome-field advantage."
A park of note is Olympic Stadium in Montreal. The park was designed with a large tower that loomed over top. Cables came down from the top of the tower to connect to the large oval center of the roof. This oval center was supposed to be lifted by the cables, opening the park up if the weather was pleasant. However, the mechanism never worked correctly, and what was supposed to be a retractable roof was initially never used and then later became permanently fixed, making the stadium a strictly indoor facility. Indoor parks faced many of the same problems of the multi-purpose parks, which was compounded with the added problem of playing an outdoors sport indoors.