GRAPEVINE -- Legoland Discovery Center, which opened in April, is planning a $1 million expansion for a new attraction: an indoor-outdoor driving course that will allow kids to help the Lego "Texas Rangers capture crooks."The Grapevine City Council approved the 8,500-square-foot expansion Tuesday and provided a $500,000 grant to pay for half of the work at Grapevine Mills mall. The attraction will open in the spring, the company announced.Iain Scouller, Legoland's general manager, said the expansion will not be the last for what has turned out to be a popular attraction for kids."We have planned to provide the best experience for the kids," Scouller said after the council's vote. "We want people to come back, so you will see something new every year -- maybe not quite this big each year, but something new."He said that adding another attraction was part of U.K.-based Merlin Entertainments Group's plans from the start."But we have been carefully evaluating what our guests want and what will help ensure our visitors will want to return again and again," Scouller said later in a statement. "Merlin is confident that the Lego City-themed driving experience will be a great addition to the already successful attraction here in Grapevine."A spokeswoman for Legoland declined to provide attendance figures for Legoland, which often has kids waiting outside the entrance for their chance to build and play in the 35,000-square-foot indoor attraction.The space cost $12 million, according to company figures.The original agreement between the city and Grapevine Mills Limited Partnership called for a $500,000 grant to help pay for Legoland's initial startup.It also spelled out an additional $500,000 grant for a prospective Lego-themed miniature golf course. With the council's action and the change to a driving course, that second grant will be awarded once the course has reached "substantial completion" and begins operation, according to the revised agreement.City Manager Bruno Rumbelow said the money comes from the tax increment financing district set up around Grapevine Mills mall. The increased property tax revenue from the mall development is spent to enhance that area.Construction on the driving course is expected to begin next month, and an opening date is planned in late April. Scouller said all the details have not been finalized. However, about two-thirds of the attraction will be in Legoland space being used for storage and the rest will extend outside the mall. The 2,500-square-foot outdoor area may be under a canopy rather than fully enclosed.As the kids drive single-seat cars around the course, they will follow a cops-and-crooks-themed story that will present about nine scenes, such as a robbery, forest bridge, ranger headquarters, abandoned mine and crooks captured."It will be interactive and family-friendly," according to the news release.Merlin Entertainments Group operates both Legoland and its companion attraction, Sea Life Aquarium, which is across the hall in Grapevine Mills.