Artificial turf is making a comeback at pro sports venues, and NFL stadiums are part of the trend. Modern technology allows newer, high-tech artificial surfaces to simulate the bounce and feel of natural grass. Synthetic surfaces also conserve water, which is environmentally friendly and saves teams money.

But not all NFL stadiums have moved away from natural surfaces. Here are six stadiums that still have natural grass.

1. Levi’s Stadium, San Francisco 49ers

The newest arena on the list, Levi’s Stadium opened in 2014 and features a Bermuda grass field. Despite being just five years old, the 49ers’ home field has been criticized for not being high-quality enough for an NFL stadium.

In a 2015 game, grass collapsed underneath Ravens kicker Justin Tucker. And former Broncos CB Aqib Talib called the field “terrible” the day after the Broncos won Super Bowl 50 at the stadium.

2. Arrowhead Stadium, Kansas City Chiefs

The home of the Chiefs since 1992, Arrowhead Stadium installed a natural grass surface in 1994 to replace the previously used Astroturf. Many believe the arena gives the Chiefs a strong home-field advantage. Fun fact: In 2013 the crowd at a Raiders-Chiefs game set what was, at the time, the Guinness world record for the loudest stadium at 137.5 decibels.

3. Soldier Field, Chicago Bears

Although Soldier Field opened in 1924, the Bears didn’t begin using it as the home field until 1971. During the team’s tenure at the stadium, it has switched between natural grass and artificial turf a few times.

It used Kentucky bluegrass from its opening until 1970, then switched to AstroTurf when the Bears moved in. The AstroTurf remained through 1987. The Kentucky bluegrass returned in 1988, and it has remained the playing surface for three decades since.

4. Heinz Field, Pittsburgh Steelers

Replacing Three Rivers Stadium, Heinz Field has served as home for the Steelers since 2001. It has Kentucky bluegrass, which has been criticized for its poor performance when the Steelers play at home following other events, like college or high school football games.

Being in a cold-weather climate, the field is heated from below to keep the surface warm enough so the grass can grow year-round.

5. State Farm Stadium, Arizona Cardinals

You may be surprised to learn that State Farm Stadium uses a grass field. Because of Arizona’s desert climate, an artificial surface would be easier to maintain, and the grass surface requires a lot of watering in the hot climate.

There is a unique feature of the grass surface used at the Cardinals’ home. It is a roll-in surface, which is removed when the stadium hosts non-sporting events. This is done to protect the natural grass and keep it in good shape for Cardinals games.

6. Lambeau Field, Green Bay Packers

The most famous NFL stadium, Lambeau Field has been the Packers’ main home since 1957. It has endured extensive renovations over the years to keep it updated without needing a new facility. The playing surface also receives occasional upgrades, most recently in 2018, when a polyethylene-based SIS Grass surface was installed.

Like in Pittsburgh, Lambeau’s playing surface is heated so the famed moniker of “the frozen tundra” is now outdated; heating the field means it no longer freezes like it used to.