I'd be happy to help create a warm, inviting description for your Hiking session! However, I don't have access to the data from the fields you mentioned (12KM and the other field). If you could share what information is in those fields, I can craft a perfect one-line description that incorporates those details along with the title and the fact that it's free and open to all.

💧 Porteu aigua, 👟 Porteu calçat esportiu adequat, 🧢 Porteu roba adequada, 🎒 Porteu una motxilla petita, 🌞 Protegiu-vos del sol, 🧥 Porteu roba per capes, 🚫 Aneu pels senders marcats, 📱 Porteu un telèfon

No s'han proporcionat més detalls específics per a aquesta activitat, la qual cosa significa que podeu presentar-vos al punt de trobada sense més instruccions.