Honestly? Most locals don't even know about it. In this part of the town forest (Stadtwald) above the famous Heidelberg castle, Sequoias have been seeded in the last quarter of the 19th century. So, locals enjoy the quiet of the town forrest in combination with the surprising discovery of foreign, non-european trees.
Take this short, relaxing hike from the Castle (a bit more ambitious from the town center). You will get a lot of quiet nature and a sound relief from the touristy side of Heidelberg. Sure, the Sequoias don't match their US relatives, but if you are a novice they are just fine. At the largest tree you can rest for a picnic (bring with you).
In the town forest, simply follow the signs Sprunghöhe (or Molkenkur first). You will find larger sandstones as signpost at all essential crossings.