Kala Patthar is one of the highest and most accessible trekking peaks in the Khumbu and one of the most spectacular viewpoints for Mt. Everest and Lotse. At 5648m (18,530 ft.), it would be a huge peak almost anywhere, but in the Khubmu, you're still more than 3000m (10,000 ft) below Everest!
The route itself is a simple hiking trail, fairly steep and well marked. Sometimes it's got some snow, but usually not by March. You could do a round trip, but I'll leave it as an ascent since most people will want to stick around up top and admire the view.
It's only a mile, but it's a tough one!