Mount Tallac is a 10 mile hike (out and back) with approximately 3500 ft of elevation gain. The main trailhead is just a few miles west of South Lake Tahoe, though this peak can also be reached from Gilmore Lake and other areas deeper in Desolation Wilderness. It’s strenuous, but the incredible views down to Fallen Leaf Lake, Lake Tahoe, and over to Desolation Wilderness make this a very popular hike. On summer weekends, there can easily be dozens of people on the summit at once. Permits for day hikes are self-issued at the trailhead. For overnight trips, reserve your permit in advance at Recreation.gov.
For more details, check out the Mount Tallac Norcalhiker blog post