Borovets is at the foot of peak Moussala (2925 m), the highest on the Balkan Peninsula.
In summer, one can do a one-day hike to Moussala, using the lift from Borovets to Yastrebets and then walking for 8 hours. The organisers recommend you to bring proper shoes and clothes and to hire a touristic guide from the hotel.
Touristic shoes are obligatory since the altitude is considerable, Yastrebets is quite far away from Moussala and the paths to there are rocky and steep. Do not forget hats, sun glasses and sun screen (although all those are also available in the shops). This excursion is not recommended to people with health problems.
Pleasant walks for less ambitious tourists are possible as well, without special touristic equipment.