Tatranska magistrala - Smokovec to Chata pri Zelenom Plese
While this trail involves a fair amount of climbing, it is not technically difficult and most of the slopes are not steep, it's mpre of a steady climb. It will take you from the town of Stary Smokovec along the slopes of Lomnicky Stit and up onto Velka Svistovka (2030m), with nice views onto the plains below. There's three mountain huts long the way - 'Zamkovskeho chata', 'Chata pri Skalnatom Plese' and 'Chata pri Zelenom Plese'.
Due to rocky terrain, hiking shoes are highly recommended.
The trail begins in the town of Stary Smokovec, which can be easily accessed by car or the High Tatras tram.
This trail begins in Starý Smokovec, where you can either hike up to Hrebienok (45min) or take the cable car up. There is a marked trail going up, but it's quicker and easier just to follow the cable car tracks. From Hrebienok, continue along the red trail to Zamkovskeho chata. While it is possible to continue along the red trail without going to Zamockeho chata, the 5min detour is highly recommended as you can get variety of refreshments there.
From Zamkovskeho Chata continue along the red trail, which will climb steadily until reaching Chata na Skalnatom Plese, and will lead you along the dwarf-pine covered slopes of Lomnicky Stit. Chata na Skalnatom Plese is an end point of the chair-lift from Tatranska Lomnica and offers various refreshments. There is a mountain lake (pleso) to see as well.
You continue along the red trail, which still climbs steadily into more rocky terrain, eventually peaking once you reach 'Velka Svistovka' (2038m) This is the highest point of the trail. Continue along the red path (there will be some very minor climbign sections) down to Chata pri Zelenom Plese. Have a beer, enjoy the views of the Zelene Pleso and surrounding peaks. From here, you begin the descent down along the valley floor. Follow yellow and then the blue trail. At Metalurg intersection swich back to yellow trail. You will end up in Tatranska Lomnica, where you can catch the tram.
You can take a detour along the green (then blue) trail from, Hrebienok and see the waterfalls of Studenovodsky potok (creek) along the way (this will set you back about 20min). The trail will cross the red trail again at a bridge across the creek, where you follow the red trail from there to Zamkovskeho chata.
From Chata na Skalnatom Plese there is also the possibility of taking the chair-lift either to Lomnicky Pass (2190m) (great views into Mala Studena Dolina), which in winter serves the skiers as well or even the separate chair-lift to Lomnicky Stit (2634m), which is the second tallest peak of high Tatras (and the most easily accessible) with great views all around. Note that this might take significant amount of time in the latter case. If you have had enough, or the time is runnign short, you can eiter hike down to Tatranska Lomnica from here along the green trail or take the chair-lift down.