The fort at Lachhmangarh sits on a rocky hill above the town, built by the town's founder Rao Raja Laxman Singh of Sikar in 1862. It is privately owned and closed to visitors, so you cannot enter the main fort complex. However, the paved ramp that winds up the hillside to a small temple near the fort entrance is accessible, and the views from this point over the town, the surrounding desert, and the scattered havelis below are excellent.
The fort's exterior walls are in reasonable condition and give a good sense of the scale of Rajput fortifications even at the level of a minor provincial town. The walk up takes about 15-20 minutes from the town center.
Even for a small town, the combination of the fort silhouette and the painted havelis below makes Lachhmangarh one of the more photogenic stops on the Shekhawati circuit.