The largest part of the island is relatively flat with plains reaching down to the sea and low mountains (the highest point being Kleidi, 320m.). That is also why it took its name from the ancient Greek word "Leros" which means smooth, flat. Dense vegetation covers a large part of the island. The landscape is made even more beautiful by plains forested with pine, eucalyptus, oak and olive trees.

It is a landscape that is constantly changing. The sea cutting sharply into it has formed at many points deep, protected harbors and large bays. The gulf of Partheni is in the northern part Leros; the islet of Archangelos lies at its entrance, protecting it from the winds. At the southern tip of the island is the long and narrow bay of Xerokambos; Kalymnos stands opposite and the Glaronisia ("Gull islands") are before it.

The island has two large harbors, Lakki to the southeast, one of the largest nature harbors in the Mediterranean, and Ayia Marina to the northeast. There are many small pictures islands surrounding it on all sides: Ayia Kyriaki, Peganousa, Farmako, Strongyli, Trypiti. Most of these are good fishing spots and the depths of the sea are of incomparable beauty, enchanting to divers. Leros has quite a number of small springs. The best known are Paliaskloupis, Kalikaris, Sykidia and Panayies.

The island has a mild and pleasant climate without great fluctuations. The incredible variety of flowers that ornament courtyards, doors and windows bears witness to that. The average summer temperature is between 20~26C while in winter it dips to 12~17C. Thus, Leros is an ideal place for holidays, no matter the season.